Problem solving and word problem resources online
Find here an annotated list of problem solving websites and books, and a list of math contests. There are many fine resources for word problems on the net! have personally checked & reviewed each website, to make sure it is truly useful.
General
Scales Problems
A video lesson that shows the solution to 14 different balance problems, starting from the most simple and advancing to some that have double scales.
/teaching/md/
The do's and don'ts of teaching problem solving
Why do most students have so much trouble with word problems? Is the reason related to onestep word problems in math textbooks?
/teaching/problem_solving.php
Growth mindset and the value of mistakes in math learning
This article discusses brain plasticity  or the huge potential for our brains to grow  which means that EVERY student CAN learn math. Students need to have a growth mindset where they value mistakes and see them as opportunities for brain growth and learning.
www.mathmammoth.com/lessons/value_of_mistakes.php
Problem solving websites
Favorite puzzles
A collection of favorite math puzzles for children, gathered from my puzzle contest. Most only require the four basic operations so work well for elementary school children and on up.
/online/
Expii Solve
Fun, thought provoking, interactive math puzzles shown through current events and pop culture designed to relate to your life.
www.expii.com/solve
Problem Solving Decks from North Carolina Public Schools
Includes a deck of problem cards for grades 18, student sheets, and solutions. Many of these problems are best solved with calculators. All of these problems lend themselves to students telling and writing about their thinking.
/teaching/problemsolvingdecks.php
Math Stars Problem Solving Newsletter (grades 18)
These newsletters are a fantastic, printable resource with a variety of different problems and their solutions.
/teaching/mathstars.php
A+ Click
A+ Click features a graduated set of over 4700 challenging problems for students in grades one through twelve, starting from the very simple to the extremely difficult. No fees, no ads, no calculators, and no sign in. The questions concentrate on understanding, spatial reasoning, usefulness, and problem solving rather than math rules and theorems. The tests adapt to student ability.
www.aplusclick.com
Variations of Sudoku from Nrich
Fun, puzzling, and engaging variations on Sudoku. For example, you are given products, differences, equations, ratios, and so on as clues to complete the Sudoku.
nrich.maths.org/public/search.php?
Word Problem Worksheets from DadsWorksheets.com
Very simple, mostly oneoperation word problem worksheets for grades 14. Some worksheets have problems for two different operations.
www.dadsworksheets.com/v1/Worksheets/Word Problems.html
MathCounts School Handbook
This handbook contains 300 creative problems for grades 68. All problems are mapped according to topic, to difficulty level, and to the Common Core State Standards.
mathcounts.org/resources/schoolhandbook
Enriching Mathematics
Openended, rich, and investigative math challenges & activities for all levels.
nrich.maths.org
Virtual Math Club
Problem sets & puzzles similar to those found on math contests such as the AMC 8, AMC 10, MATHCOUNTS, or the middle school math olympiads, including answers and video solutions posted a week later. For middle school/early high school level.
virtualmathclub.wordpress.com
Primary Grade Challenge Math by Edward Zaccaro
A good book on problem solving with very varied word problems and strategies on how to solve problems. Includes chapters on: Sequences, Problemsolving, Money, Percents, Algebraic Thinking, Negative Numbers, Logic, Ratios, Probability, Measurements, Fractions, Division. Each chapter’s questions are broken down into four levels: easy, somewhat challenging, challenging, and very challenging.
Thinking Blocks
Learn to model or make visual representations of word problems with this interactive program.
www.mathplayground.com/thinkingblocks.html
Math Circle Presentations
Math circle presentations for grades 612 from University of Waterloo and their related student exercises, available as PDF files. These can be used as enrichment, as challenging word problems or as review of certain topics.
cemc.math.uwaterloo.ca/events/mathcircle_presentations.html
Figure This! Math Challenges for Families
Word problems related to real life. They don't always have all the information but you have to estimate and think. For each problem, there is a hint, other related problems, and interesting trivia. Website supported by National Council of Teachers of Mathematics.
www.figurethis.org
Problem Solving Skills tutorial
This is an overview of problem solving skills that you can use to attack problems in many areas of life. Includes tips and ideas such as: ask the right questions, slow down, make sure you're solving the right problem, assessing the situation, and so on.
ryanstutorials.net/problemsolvingskills
Learn to Solve Word Problems
A collection of school algebra word problem solvers that solve your problems and help you understand the solutions. All problems are customizable, meaning that you can change all parameters.
www.algebra.com/algebra/homework/word
Math
Word Problems for Children  MathStories.com
Over 12,000 interactive and noninteractive NCTM compliant math word problems, available in both English and Spanish. Helps elementary and middle school children boost their math problem solving and criticalthinking skills. Need to pay for membership.
www.mathstories.com

Word Problems Solving Strategies
Gives one example of each strategy: Find a pattern, Make a table, Work backwards, Guess and check, Draw a picture, Make a list, Write a number sentence, Use logical reasoning.
www.mathstories.com/strategies.htm
Problem Makeovers by Dan Meyer
Textbook problems that have been changed to be more open and inviting for student exploration.
blog.mrmeyer.com/category/makeovermonday/
MathsChallenge.net
Search for number, geometry, probability etc. word problems and challenges. Includes solutions.
mathschallenge.net
Noetic Learning Challenge Math
This is a program with weekly assignemts, designed to hone young students' mathematical problem solving skills and logical reasoning skills. The problems are nonroutine problem solving questions that are adapted to many math competitions. Price is about $20 for a semester.
https://www.noeticlearning.com/gifted/index.jsp
Archive for the Handley Math Page Problems of the Week
From 1998 till 2005  lots of good problems with solutions.
www.pleacher.com/handley/probweek/probarch.html
Best Articles about Solving Word Problems from Let's Play Math
A collection of the best problem solving articles from Let's Play Math blog. Many of these explain and use the bar diagram method also found in Singapore Math books.
letsplaymath.net/2010/05/24/
Ms. Lindquist: the Tutor
An intelligent tutoring system for algebra for tutoring students
in writing expressions for algebra word problems.
www.cs.cmu.edu/~neil
Books
Ratios, Proportions, and Problem Solving 
Primary Grade Challenge Math by Edward Zaccaro
A very good book on problem solving with very varied word problems and strategies on how to solve problems. Includes chapters on: Sequences, Problemsolving, Money, Percents, Algebraic Thinking, Negative Numbers, Logic, Ratios, Probability, Measurements, Fractions, Division. Each chapter’s questions are broken down into four levels: easy, somewhat challenging, challenging, and very challenging. 

Challenge Math For the Elementary and Middle School Student by Edward Zaccaro Another problemsolving book by Zaccaro, for middle school levels. It contains both lessons and exercises for problem solving with three levels of questions. 
Math Puzzles and Brainteasers
A book with over 300 delightful puzzles and problems that teach math and problem solving.
www.amazon.com
EvanMoore Daily Word Problems, grades 16
Browse Amazon's collection of EvanMoore Daily Word Problem books for grades 16, which can be used to supplement any math curriculum. The problems are realistic, often challenging, and cover a good variety of topics for the given grade level.
www.amazon.com
Ray's Arithmetic (free download)
This old arithmetic book bases its instruction on word problems, starting with 1st grade addition and subtraction problems, and advancing through the topics until percentage. One could use it to help children solve word problems, since it starts from the simplest kind of word problems, and gradually advances. Read online or download for free; the links are in the left sidebar.
www.archive.org/details/raysarithmeticse00rayjrich
A Middle School Math Workbook: PreAlgebra, Algebra I, and Geometry by Qishen Huang
This book contains challenging problems that will help your child gain math skills at an internationally competitive level.
www.amazon.com/gp/product/0981907245
A High School Math Workbook: Algebra, Geometry & Precalculus by Qishen Huang
This book contains challenging problems that will help your child gain math skills at an internationally competitive level.
www.amazon.com/HighSchoolMathWorkbookPrecalculus/dp/0981907253
Contests and similar
"Problem of the Week" (POWs)
Problem of the week contests are excellent for finding challenging problems and for motivation. There exist several:
Math Forum: Problem of the Week
Five weekly problem projects for various levels of math. Mentoring available.
mathforum.org/powsMath Contest at Columbus State University
Elementary, middle, algebra, and "general" levels.
themathcontest.comProblem of the Week at University of Waterloo
Each week, problems from various areas of mathematics will be posted here and emailed to teachers for use with their students in Grades 7/8, 9/10, and 11/12. In addition, there are hundreds of archived contest problems, math circle presentations and exercises.
cemc.math.uwaterloo.ca/resources/potw.phpMath Olympiads
A math problem solving competition for teams (groups of students) from schools or home schools. For grades 48.
www.moems.orgAmerican Mathematics Competitions
America’s longestrunning math contests. There is one for middle school students and two for high school students.
www.maa.org/mathcompetitionsPaul Erdos International Math Challenge
This is open to any child in three different age groups.
inside.gcschool.org/abacus/MathCounts Problem of the Week
Every week, a new and fun problem to solve! Browse the archives to find more problems.
mathcounts.org/resources/problemoftheweek
Mathathlon
Mathlathon is a monthly online math contest for students in grades 310. It is free if you have a subscription to Math Buddy; otherwise it costs $9.99 a year. I have checked the free sample contest for grade 6 and liked it really well! The questions are designed to foster intuition and problem solving skills.
www.mathlathon.org/mathlathon/index/
Math League Contests
Get access to a vast online practice area and enroll in the official 20142015 Online Math League competitions. Contests are available from grade 2 through algebra. Involves a registration fee.
www.onlinemathleague.com
National Math Bee
Online math tournament in which students in grades one through six compete in any or all of the four basic operations: addition, subtraction, multiplication, and division.
nationalmathbee.org
Math projects or investigations
Mixing in Math
A list of activities that mix math in to sports, snack time, arts and crafts, playground games etc. Easy to prepare and lead, and free.
mixinginmath.terc.edu
Yummy Math
Quality math activities from real life, organized into categories such as math and social studies, geometry, data and probability, holidays and annual events, food, sports, number sense, etc. Available as PDF and DOC files. The activities are free but answers are available only to subscribers.
www.yummymath.com
Make It Real Learning
Math projects or activitity worksheets of reallife applications, focused on answering the question, "When am I ever going to use this?" Free samples available.
www.mathmammoth.com/worksheets/mirl
MathNotations
A blog with quality math investigations and projects for middle and high school level.
mathnotations.blogspot.com
Math Projects.com (MPJ)
Powerful and innovative math projects, lesson plans, and thoughtprovoking articles, from prealgebra through geometry.
www.mathprojects.com
Middle School Math Projects
Quality math projects, spanning from number sense, geometry, statistics, probability, algebra, to special math events. Pricing $7 on up.
www.digitallesson.com
The Math Academy
Downloadable booklets that include handson activities about reallife applications of mathematics. Includes probability, fractions & percents, statistics, combinatorics, and patterns & functions.
www.actuarialfoundation.org/mathacademy/
RealLife Math Vol. 1 PDF download
A collection of activities for grades 68 of how math is used in real life. All twelve lessons include a teacher's guide that explains how to conduct the activity and a student worksheet that guides the student and poses problems. Price: $9.99. Free example pages included.
makemathmore.com/reallifemath
Math Activities and Games at Education.com
A huge list of free math activities, organized by grade level from kindergarten through high school.
www.education.com/activity/math
Mathwire.com
Innovative and creative board games, activities and worksheets for elementary and middle school math topics.
www.mathwire.com
Handson Manipulative Instructions
Print, cut out, and color & glue  various blocks, tiles, graph paper.
mason.gmu.edu/~mmankus/Handson/manipulatives.htm