What is reasonableness?
To be reasonable means to be as much as is appropriate or fair.
In math, reasonableness can be defined as checking to verify that the result of the solution or the calculation of the problem is correct or not, be either estimating or by plugging in your result to check it.
When solving a math problem, we can check if the answer we have derived to is reasonable or not, based on an estimate. A reasonable estimate does not exceed the original numbers in a problem.
For instance, in a division problem like 424 ÷ 4 − 10, we can check is our answer is reasonable or not, by estimating an approximate answer or by plugin gin using the division formula.
We can round down 424 to the nearest hundreds, to estimate the answer. Since 96 (actual answer) ≈ 90 (estimate answer), we know our solution is correct.
We can check our solution by plugging in to verify using, 96 × 4 + 10 as well.
Let's do it!
While solving word problem, ask your child to check the reasonableness of his/her answer. It might feel like doing double work at first, but it will help the child to make sure his/her answer is correct.
You can also ask your child to check the reasonableness of the bill when you dine out or while shopping.
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