Rounding/Estimating
17 rounded to the nearest tens
What is: 20.
The library own 413 books and there are 365 books checked out. How many books are still at the library?
There are 48 books still in the library.
What is 9 x 7?
63
What is 84÷7?
84÷7 = 12
The toy store has 4 times as many whistles as yo-yos. Write a multiplication expression to represent the number of whistles compared to yo-yos.
4 x 7 = r
232 rounded to the nearest tens
What is: 230.
What addition equation can be used to find the next number in the pattern:
9, 18, 27, 36, 45, ...
45 + ____ = _____
45 + 9 = 54
Jameson's dog, Bailey, eats 28 cups of food in a week. Bailey eats the same amount of food each day.
Eason's dog, Lucky, eats 21 cups a week.
In one day, how many more cups of food will Jameson's dog, Bailey, eat than Eason's dog, Lucky?
1 more cup: Lucky will eat 3 cups a day (21÷7 = 3) and Bailey will eat 4 cups a day (28÷7= 4). So, 4-3 = 1. Bailey will eat 1 more cup a day than Lucky.
What is 490 ÷ 7?
If 49 ÷ 7 is 7, then 490 ÷ 7= 70.
Eason is thinking of a number between 60 and 80. The number is a multiple of 2 and a multiple of 9. Which number is it?
74
A number that is a multiple of both 2 and 9 is a multiple of their least common multiple (LCM), which is 18.
The multiples of 18 between 60 and 80 are:
Rounding numbers to estimate the sum of 73 + 21
What is the difference of: 659 - 318?
Part A: Which equation models the most reasonable estimate of the difference?
a. 600 - 300 = 300
b. 625 - 320 = 305
c. 660 - 320 = 340
d. 700 - 300 = 400
PART B
What is the exact difference?
PART A:
b. 660 - 320 = 340 because rounding to the nearest tens will give me a closer answer than rounding to the nearest hundreds.
PART B:
The exact difference is: 341
Evie packs 3 boxes. She puts 3 lunch bags in each box. There are 4 sandwiches in each lunch bag (Evie is nice and bringing extra food for friends). How many sandwiches will Evie pack?
Evie will pack 36 sandwiches.
At Gabriel's soccer practice, the soccer balls are stored in bags. In one back, there can be 8 soccer balls. He has to put away 32 balls all together. How many bags will Gabriel need to use?
Gabriel will need to use 4 bags because: 32÷8 = 4.
A school has 3 classes. Each class has 25 students. Each student brings 2 books to school. How many books are brought to school in total?
Total number of students:
25 x 3 OR (20 x 3 = 60. and 5 x 3 = 15) so 60+15 = 75
So there are 75 students.
Total number of books:
75 x 2 OR (70 x 2 = 140. and 5 x 2 = 10) so 140+10 = 150.
Estimate the sum of:
393 + 225
1. 393 -> 390 and 225 -> 230: 390+230 = 620
OR
2. 393 -> 400 and 225 -> 200:
400 + 200 = 600
The pet shelter bought 85 pound of dog food, 50 pounds of cat food, and 15 pounds of gerbil food. How many pounds of animal food did the pet shelter buy?
150 pounds of pet food.
Winnie and Yuvika are setting up chairs for a school event. Winnie sets up 45 chairs, and Yuvika sets up 30 chairs. Later, they realize that 15 chairs are damaged and need to be removed. After removing the damaged chairs, they arrange the remaining chairs into rows with 6 chairs in each row.
How many rows of chairs do they set up?
Subtract the damaged chairs:
45+30=75(total chairs)
75−15=60 (remaining chairs)
Divide the remaining chairs into rows:
60÷6=10
There will be 10 chairs in one row.
Aviel and Jamie are collecting canned goods for a food drive. Aviel collected 38 cans, and Jamie collected 25 cans. They divided the cans equally into boxes, with 7 cans in each box.
How many boxes did they need?
They will need 9 boxes.
Hrehan is making a garden. He is using 9 pieces of fence for the length of the garden. For the width of the garden, he uses 4 pieces of fence. What is the area of the garden?
Hint: Area is the inside space of the garden. You will use multiplication or division.
9 x 4 = 36. The area will be 36 (feet)
Kaitlyn sold 336 muffins at the bake sale. Hrehan sold 287 muffins. Hrehan estimates that he sold 50 fewer muffins than Kaitlyn. How did he estimate?
Hrehan rounded to the nearest 10. He rounded 336 to 340 and 287 to 290. Then, he subtracted: 340-290 = 50.
What is the unknown number and what property did you use to solve it?
(p + 8) + 32 = 49
Katherine, Evie, and Kaitlyn are baking cookies for a bake sale. Katherine bakes 24 cookies, Evie bakes 36 cookies, and Kaitlyn bakes 30 cookies. They decide to give away 18 cookies to a local shelter before packaging the rest. Then, they pack the remaining cookies into boxes, with each box holding 6 cookies.
How many boxes do they use?
Add the total cookies baked:
24+36+30=90
Subtract the cookies given away:
90−18=72
Divide the remaining cookies into boxes:
72÷6=12
They use 12 boxes.
Sahasya, Morgan, and Leo are stocking shelves at the HES library. Sahasya puts away 36 books, Morgan puts away 48 books, and Leo puts away 24 books. Later, they realize 12 books are from the Harvard Public Library, not the HES library, so they put them aside to bring across the street. The remaining books that belong at the HES library are divided evenly onto 12 shelves.
How many books are on each shelf?
Add the total books put away:
36+48+24=108
Subtract the books in the wrong section:
108−12=96
Divide the remaining books onto the shelves:
96÷12=8
8 books are on each shelf.
Invitations cost $3 for a pack of 8. Aviel gives the cashier $20 to buy invitations and gets $11 in change. How many packs of invitations does Aviel buy? Explain.
Here's how we solve the problem step by step:
Determine how much Aviel spends:
Find the cost of one pack:
Calculate the number of packs:
So, Aviel buys 3 packs of invitations.