Estimation in Word Problems
Basics on the topic Estimation in Word Problems
***Estimation in Word Problems
In word problems, checking our work for reasonableness is a useful skill. We can use estimation strategies such as rounding or compatible numbers with mental computation. First, read and then reread the problem to identify the numbers used for computation. Then, use rounding or compatible numbers. Next, use mental math to find an estimate. Finally, compare the estimation to the original answer to determine reasonableness. If the numbers are close, your math is most likely correct. If the numbers are far apart, your math most likely has a mistake and needs to be corrected.
Transcript Estimation in Word Problems
Welcome to 'Sense or No Sense!' Mr. Squeaks and Imani must determine the reasonableness of answers to word problems! In order to win the prize, they will need to use "Estimation in Word Problems." In word problems, checking our work for reasonableness is a useful skill. We can use estimation strategies such as rounding or compatible numbers and mental computation. First, read and then reread the problem to identify the numbers used for computation. Then, use rounding or compatible numbers. Next, use mental math to find an estimate. Finally, compare the estimation to the original answer to determine reasonableness. If the numbers are close, your math is most likely correct. If the numbers are far apart, your math most likely has a mistake and needs to be corrected. Here's the first question. Axel and Tank plan a family trip to Submersive Studios. Admission is sixtyseven dollars and ninetynine cents for adults, and fortytwo dollars and ninetynine cents for children. Four adults and two children are going. Axel says it will cost three hundred fiftyseven dollars and ninetyfour cents altogether. Does his answer make sense...or no sense? To determine the reasonableness of this answer, they will estimate. Sixtyseven dollars and ninetynine cents is rounded to seventy dollars. There are four tickets at this price. Seventy times four equals two hundred eighty. Fortytwo dollars and ninetynine cents is COMPATIBLE with fortyfive. Fortyfive times two is ninety. Two hundred eighty plus ninety equals three hundred seventy dollars. Three hundred seventy dollars is close to three hundred fiftyseven dollars and ninetyfour cents, so Axel's answer is reasonable. " SENSE!" The next round is worth DOUBLE and here is the question! Zuri and Freddie collected cans to recycle. Zuri collected six boxes with twentyfour cans in each. Freddie collected four boxes with thirtyseven cans in each. Freddie says he collected two hundred ninetytwo MORE cans than Zuri. Does his answer make sense... "SENSE!" Mr. Squeaks answered incorrectly because he rushed and didn't check reasonableness. Here is how estimation would have helped. Zuri had six boxes of twentyfour cans. What number is COMPATIBLE with twentyfour? Twentyfive. What is six times twentyfive? One hundred fifty. Freddie had four boxes of thirtyseven cans. What number do we round thirtyseven to? Forty. What is four times forty? One hundred sixty. The question asks how many MORE, so we subtract. What is one hundred sixty minus one hundred fifty? Ten. Freddie's answer was NOT reasonable because he used addition instead of subtraction. It's the final round they must get this correct or leave emptyhanded! Nari and Gus are planning a cookout. They invited twentyeight guests and want to have enough for two hot dogs each. Hot dogs come in packs of twelve. Nari says they need to buy five packs. Does his answer make sense...or no sense? Pause the video and solve this problem to see what they SHOULD answer and press play when you are ready for the solution! Twentyeight rounds to thirty. Thirty times two equals sixty. Twelve and five ARE compatible numbers, so multiply them together to get sixty. While they debate their answer, let's review! Remember, In word problems, checking our work for reasonableness is a useful skill. First, read and reread the problem to identify the numbers used for computation. Then round or change the larger numbers to compatible numbers. Next, use mental math to find an estimate. Finally, compare the estimation to the original answer to determine reasonableness. Congratulations Imani and you too, Mr. Squeaks!
Estimation in Word Problems exercise

Outline the steps for checking a word problem.
HintsIn any process, the first step is always to look at, observe, or read the information.
When solving a math problem, calculating the answer always comes before checking the answer.
SolutionWhen using estimation in word problems:
 First read, then reread the problem, to identify the numbers used for computation.
 Second, use rounding or compatible numbers to simplify the problem.
 Third use mental math to find an estimate.
 Last compare the estimate to the original answer to determine if it is reasonable, or not.

Is the answer reasonable, or not?
HintsWhen rounding up or making compatible numbers always estimate to the closest 5 or 10.
Examples:
17 becomes 20.
63 becomes 65.Compare your estimation to the original answer to determine if it is reasonable or not.
If the answers are close, then the original answer is reasonable.If there is a large difference, more than 20 or so, then it is not reasonable.
Solution Zuri collected 6 boxes with 24 cans in each.
6 x 25 = 150 Freddie collected 4 boxes with 37 cans in each.
4 x 40 = 160 Freddie has about 160 cans.
160  150 = 10.
Freddie has about 10 cans more than Zuri. Freddie's claim that he collected 292 more cans than Zuri is not reasonable.

Determine how to solve the word problem.
HintsWhen rounding up or making compatible numbers always estimate to the closest 5 or 10.
Examples:
17 becomes 20.
63 becomes 65.The word each in a word problem signals that multiplication should be used.
Each of Bill's 23 guests receives 2 small toys.
23 x 2 = the number of toys Bill and Marty need to buy.There is only one correct choice.
Solution Bill invited 23 guests, so round 23 up to 25 to make it friendlier.
 Bill wants to give 2 small toys to each guest, so multiply 25 by 2.
 2 x 25 = 50.
 Bill and Marty need to buy about 50 small toys for the gift bags.

Solve the word problem using estimation.
HintsWhen rounding or making compatible numbers always estimate to the closest 5 or 10.
Examples:
17 becomes 20.
63 becomes 65Compare your estimation to the original answer to determine if it is reasonable or not.
If the answers are close, then the original answer is reasonable.If there is a large difference, more than 20 or so, then it is not reasonable.
Solution1) $5.85 can be rounded down to $5.00.
$14.90 can be rounded up to $15.00.
2) $5.00 x 11 = $55.00.
$15.00 x 10 = $150.00.
3) $55.00 + $150.00 = $205.00.
Marie's guess of $300.00 for flowers does not make sense.

Use mental math to make compatible numbers.
HintsWhen rounding up or making compatible numbers always estimate to the closest 5 or 10.
Examples:
17 becomes 20.
63 becomes 65.When rounding up or making compatible numbers with money, always eliminate the cents and work only with full dollars.
Examples:
$7.83 becomes $10.00.$22.99 becomes $25.00.
Solution $67.99 is rounded up to $70.00.
 $53.99 is rounded up to $55.00.
 $38.99 is rounded up to $40.00.
 $42.99 is rounded up to $45.00.

Use estimation to solve the word problem.
HintsWhen rounding up or making compatible numbers always estimate to the closest 5 or 10.
Examples:
17 becomes 20.
63 becomes 65To find how many pens Drew needs in total, multiply 10 (each person gets 10 pens) by the number of people who need them. Use the rounded number to make the problem friendlier!
To find how many packs of pens Drew needs, take the total number of pens needed and divide by 5. (There are 5 pens in each pack).
For the final question, write either 'reasonable' or 'not reasonable'.
Solution 4 people can be rounded up to 5 to make the number friendlier.
 10 pens x 5 people = 50.
 50 pens ÷ 5 = 10.
 Drew's guess that he needs 10 packs of pens is reasonable.
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