All the solutions provided in McGraw Hill Math Grade 5 Answer Key PDF Chapter 2 Lesson 8 Estimate Products will give you a clear idea of the concepts.
McGraw-Hill My Math Grade 5 Answer Key Chapter 2 Lesson 8 Estimate Products
Math in My World
Example 1
A pet store has 12 gecko lizards for sale. Each gecko lizard costs $92. About how much money would the store make if it sells all 12 gecko lizards?
Estimate the product of 92 and 12.
One Way Round one factor.
THINK It is easier to compute 92 × 10 than 90 × 12.
By rounding one factor, the estimate is ____
Another Way Round both factors.
By rounding both factors, the estimate is ____.
Answer:
By rounding one factor, the estimate is 920
By rounding both factors, the estimate is 900.
Another Way Use compatible numbers.
By using compatible numbers, the estimate is _____
Use a calculator to multiply 92 × 12. What do you get? ____
Answer:
By using compatible numbers, the estimate is 9000.
Use a calculator to multiply 92 × 12. The answer is 1104.
Circle whether the estimates were all less than or greater than the actual product.
less than greater than
the estimate is 920 is less than the actual product.
the estimate is 900 is less than the actual product.
Guided Practice
Estimate by rounding or using compatible numbers. Show how you estimated.
Question 1.
Round both factors.
The product is about ____
Answer:
The product is about 600
Explanation:
Talk Math
Show two different ways you could estimate 312 × 18.
Question 2.
Use compatible numbers.
The product is about ____
Answer:
The product is about 8000.
Explanation:
Independent Practice
Estimate by rounding. Show how you estimated.
Question 3.
Answer:
1308
The estimation by rounding is 1300.
Explanation:
Given multiplicand is 218 and the multiplier is 6.
By multiplying the both multiplicand 937 and multiplier 6, we get the value as 1308.
Question 4.
Answer:
476. The estimation by rounding the number is 480.
Explanation:
Given multiplicand is 68 and the multiplier is 7.
By multiplying both multiplicand 68 and multiplier 7, we get the value 476.
Question 5.
Answer:
3799
The estimation by rounding the answer is 3800.
Explanation:
First, start with units first. So multiply 9 by 1. Then move on to the tens digit. So multiply 9 by 3. Next move on to hundreds place then multiply 9 by 1.
Next, repeat the same with number 2.
By multiplying both multiplicand 131 and multiplier 29, we get the value 3799.
Question 6.
61 × 68 ≈ ___
Answer:
4148
The estimation by rounding the answer is 4150.
Explanation:
First, start with units first. So multiply 8 by 1. Then move on to the tens digit. So multiply 8 by 6. Continue the same process with digit 6.
By multiplying both multiplicand 61 and multiplier 68, we get the value 4148.
Question 7.
79 × 56 ≈ ___
Answer:
4424
The estimation by rounding the answer is 4420.
Explanation:
By multiplying both multiplicand 79 and multiplier 56, we get the value 4424.
Question 8.
392 × 46 ≈ ___
Answer:
18032
The estimation by rounding the answer is 18030.
Explanation:
By multiplying both multiplicand 392 and multiplier 46, we get the value 18032.
Estimate by using compatible numbers. Show how you estimated.
Question 9.
Answer:
The multiplication of the given number is 5512. The estimated answer is 5500.
Explanation:
Now use compatible numbers
That is 110 × 50
Then the answer is 5500.
Question 10.
Answer:
198
The estimated answer by using compatible numbers is 200.
Explanation:
Now use compatible numbers
That is 30 × 6
Then the answer is 180.
Question 11.
Answer:
1016
The estimated answer is 1100.
Explanation:
Question 12.
33 × 84 ≈ ___
Answer:
2772.
Explanation:
By multiplying both multiplicand 33 and multiplier 84, we get the value 2772.
Question 13.
450 × 21 ≈ ___
Answer:
9450
Explanation:
By multiplying both multiplicand 33 and multiplier 84, we get the value 2772.
Question 14.
729 × 42 ≈ ___
Answer:
30618
Explanation:
By multiplying both multiplicand 729 and multiplier 42, we get the value 30618.
Problem Solving
Question 15.
The table shows the number of pounds of apples that were harvested each day. Estimate how many pounds of apples were harvested altogether by rounding. Show how you estimated.
Answer:
The total apples that were harvested altogether are 2163.
By rounding the number of pounds the estimated answer is 2160.
Explanation:
Given
The pounds of apples are 514 + 487 + 349 + 421 + 392 = 2163.
The estimated answer is 2160.
Question 16.
In one week, a campground rented 18 cabins at $225 each. About how much did they collect in rent altogether? Show how you estimated.
Answer:
$4050
Explanation:
In one week, a campground rented 18 cabins at $225 each
Find 18 × 225
4050
The rent they collected altogether is $4050.
Question 17.
The average weight for a guinea pig is 2 pounds. The average weight for a pot belly pig is 45 times greater than the guinea pig. About how much does an average pot belly pig weigh? Show how you estimated.
Answer:
90 pounds.
Explanation:
Given,
The average weight for a guinea pig is 2 pounds.
The average weight for a pot belly pig is 45 times greater than the guinea pig.
So, 2 × 45 = 90 pounds.
Hot Problems
Question 18.
Mathematical PRACTICE 2 Use Number Sense Use the digits 1, 3, 4, and 7 to create two whole numbers whose product is estimated to be about 600.
Answer:
34 and 17 are two numbers created from the given digits whose product is estimated to be about 600.
Explanation:
Let us assume 34 and 17 are two whole numbers from the given digits.
If we multiply 34 and 17 then the answer is 34 × 17 = 578. If we are rounding up to the nearest hundreds we will get 600.
If we are rounding up the whole numbers the estimation of 34 to the nearest ten is 30 and 17 to the nearest ten is 20
Then the product is 30 × 20 = 600
Hence both the ways 34 and 17 are for the estimated product to be 600.
Question 19.
? Building on the Essential Question When is the estimation of products a useful tool?
Answer:
When the numbers we have are either bigger or smaller and when we buy multiple items which have the same price.
McGraw Hill My Math Grade 5 Chapter 2 Lesson 8 My Homework Answer Key
Estimate by rounding or using compatible numbers. Show how you estimated.
Question 1.
Answer:
96
Explanation:
By multiplying both multiplicand 4 and multiplier 24, we get the value 96.
Question 2.
Answer:
5928
Explanation:
By multiplying both multiplicand 76 and multiplier 78, we get the value 5928.
Question 3.
Answer:
13716
Explanation:
By multiplying both multiplicand 508 and multiplier 27, we get the value 13716.
Problem Solving
Question 4.
For a school assembly, students sit in chairs that are arranged in 53 rows. There are 12 chairs in each row. About how many students can be seated? Show how you estimated.
Answer:
636
Explanation:
The given question is students sit in chairs that are arranged in 53 rows.
There are 12 chairs in each row.
53 × 12 = 636
There are 636 students who would be seated
Question 5.
Klara bought a dozen bags of bird food for $27. Use compatible numbers to find the approximate cost of six dozen bags of bird food. Show how you estimated.
Answer:
$160 would cost for six dozen bags of bird food.
Explanation:
Klara bought a dozen bags of bird food for $27
12 dozen = $27 of bird food = 1 bag
24 dozens = $54 of bird food = 2 bags
36 dozens = $81 = 3 bags
48 dozens = $108 = 4 bags
60 dozens = $135 = 5 bags
72 dozens = $162 = 6 bags
Hence $160 would cost for six dozen bags of bird food.
Question 6.
Mathematical PRACTICE 3 Find the Error Rico is estimating 139 × 18. Find his mistake and correct it.
100 × 10 = 1,000
Answer:
2800
Explanation:
The given question is Rico is estimating 139 × 18.
We are here to find the mistake in the given question.
Rico has rounded down 139 to 100 and 18 to 10
Hence 140 × 20
2800
Vocabulary Check
Fill in the blank with the correct term or number to complete the sentence.
Question 7.
Compatible numbers are numbers in a problem that are easy to compute ____.
Answer:
Add, subtract, multiply or divide mentally.
Explanation:
Compatible numbers are numbers in a problem that is easy to compute Add, subtract, multiply or divide mentally.
Test Practice
Question 8.
On a cross-country vacation, Maria filled her 14-gallon gas tank eleven times. Which is the best estimate of how many gallons of gas she put in the tank altogether?
A. 75 gallons
B. 150 gallons
C. 200 gallons
D. 225 gallons
Answer:
150 gallons
Explanation:
Maria filled her 14-gallon gas tank eleven times
14 × 11
154
It is rounded to 150
The best estimate of gas she put in the tank altogether is 150 gallons.