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Learning Objective/s
Estimate the product of three- to four-digit numbers by two- to three-digit numbers with reasonable results.
Success Criteria
The learners are able to:
Demonstrates the ability to choose appropriate estimation strategies (e.g., rounding, compatible numbers).
Discussions
Think and Understand:
Sometimes, you make an estimate if the exact answer is not necessary. For
example, when you go to a grocery store, you try to make an estimate on how
much your grocery bill would cost. Also, when you buy your food in the school
canteen, you make an estimate to see if your money is enough.
An estimate is a number that is close enough to the actual number. The
word “about” indicates estimation.
To estimate products, simply round the factors to the place value that will
make computation easier.
Example 1. Estimate the product of 316 and 98.
Solution:
To estimate the product, round each factor to the nearest hundred and
then multiply the result.
Example 2. Solve and answer the given problem.
Bastian entered the auditorium and noticed that it was almost full.
There were 18 rows of chairs. He counted the number of chairs in each row.
Looking around, he noticed that the number of people vary from row to
row, but 27 seems to be the average. About how many people were there in
the auditorium?
Solution:
To estimate the answer, round 18 and 27 to the nearest ten and then
multiply the result.
Example 3. Solve and answer the given problem.
The generous homeowners bought 112 sacks of premium quality rice
at ₱1 800.00 each and donated them to the poor families in the community.
About how much did they spend for the rice?
Solution:
To fi nd the exact amount spent, multiply 112 and 1 800. To estimate the
answer, round up 1 800 to the nearest thousand and then multiply by 112 to
get the answer.
When estimating how much something will cost, it is best to round up the
unit cost so that you will have enough money with you when you go to the
store.
Cross Curricular Link
Math - Estimating products of numbers mental, computation and estimation strategies including rounding.
Real- Life Application
When shopping, estimating products can be useful to quickly calculate approximate costs. For example, if a child wants to buy multiple items, estimating the total cost can help them decide if they have enough money
Evaluation
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