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The ideas in this multiplication lesson are taken from Division 2 ebook. Only a few examples of each problem type are shown; you should make more problems of each kind for the student. Estimating products
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Estimate first and use that to check the
result. 8 × 67 = ?
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Before we start using estimation as a checking method, let's review the rounding rules. When rounding to nearest ten,
The symbol ≈ is used to indicate rounding, and is read as "is approximately" or "is about".
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Example problems
1. First estimate the result by rounding the second factor. Then multiply to find out the exact result.
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2. These word problems illustrate some situations where you can use
estimation.
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a) 58 people are invited to the party; you are going to the store to buy supplies. You figure that for each person you need two cups, two plates, and three napkins. How many cups, plates, and napkins do you approximately need?
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e) A can of beans costs 29 cents. A bag of lentils costs 42 cents. Estimate which is cheaper: to buy 8 cans of beans or to buy 5 bags of lentils.
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| h) Jill needs 21 inches of material to make a skirt. About
how much should she buy for seven skirts?
Now, add to the answer above 10 inches to make sure she has enough. The material costs 1 dollars per each 9 inches (or 4 dollars a yard). How much will it cost Jill to buy what she needs? Draw a picture! You can for example mark the 9-inch strips in your picture and use that to help.
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| i) What if you have a situation similar to the one in a) but just
with 92 people. How many cups, plates, and napkins would you
need? How many packages of each would you buy?
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Next lesson: Division as repeated subtraction (introduction to long division)
The fast, FUN, and easy way to learn multiplication. Learn the upper times tales in two sittings using mnemonic stories.
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