Rounding 10/100
What is 37 rounded to the nearest 10?
40
243 + 326 = N
N = 569
84 - 53 = N
N = 31
Mrs. B made 64 Halloween cookies on Saturday morning. She made 52 more cookies on Sunday morning. She actually didn't eat any of them! How many cookies does she have to bring to school for the teachers on Monday?
Equation with a variable, solution with a label and be ready to explain your reasoning.
64 + 52 = N N = 116 cookies
To find the total number of cookies, I have to add the number of cookies made on Saturday to the number of cookies made on Sunday.
Estimate the sum of 537 + 394 to the nearest 100.
Use your math language to explain your reasoning.
537+ 394 is about 900 / 500+400=900
537 to the nearest 100:benchmarks are 500 and 600 and 550 is the midpoint. 537 rounds down to 500 because it is less than the midpoint.
394 to the nearest 100:benchmarks are 300 and 400 and 350 is the midpoint. 394 rounds up to 400 because it is greater than the midpoint.
What is 84 rounded to the nearest 10?
80
53 + N = 163
Be ready to explain your thinking.
N = 110
62-47 = N
N = 15
325 people signed up for the River Hill pool party. There were 177 adults on the sign-up list. How many children signed up?
Equation with a variable, solution with a label and be ready to explain your reasoning.
325 - 177 = N
N = 148 children
To find the number of children at the pool party, I have to subtract the number of adults from the total number of people. The difference is the number of children.
Central Elementary School held a concert. 225 girls and 289 boys attended the concert. Katherine said about 400 students attended the concert. Do you agree? Explain why or why not.
225 rounds to 200
289 rounds to 300
200 + 300 = 500
What is 356 rounded to the nearest 10?
360
N + 135 = 449
Be ready to explain your thinking.
N = 314
147 - 56 = N
N = 91
Maria babysat all summer and saved $524. She bought a new watch and now has $189. How much did she spend on the watch?
Equation with a variable, solution with a label and be ready to explain your reasoning.
524 - 189 = N N = $335 for the watch
To find how much she spent on the watch I will have to subtract how much she had left from the total amount that she had saved. The difference is what she spent on the watch.
Deana didn’t do her homework because she said it was impossible to round 196 to the nearer ten. Do you agree with Deana? Use what you know about rounding to explain your reasoning.
I do not agree with Deana.
The nearest 10 benchmarks for 196 are 190 and 200 with a midpoint of 195. 196 is greater than the midpoint of 195 so it would round to 200 (to the nearest 10)
What is 483 rounded to the nearest 100?
500
746 + 385 = N
N = 1,131
395 - 248 = N
N = 147
At 7:00 a.m., 478 people were ready to begin the Clarkton marathon. By 10:30 a.m., 239 people had finished. How many people were still running in the marathon?
Equation with a variable, solution with a label and be ready to explain your reasoning.
478 - 239 = N N = 239 still running
To find the number of people still running I have to subtract the people who had finished from those at the start. The difference is the number of people still running.
Louis has 76 stickers and his sister has 52 stickers. They want to put all of their stickers in a sticker album. Louis says they need an album that holds at least 300 stickers. Do you agree? Why or why not?
76 is about 80 and 52 is about 50.
80 + 50 = 130
An album that held 300 stickers is more than double what they would need for all their stickers.
What is 247 rounded to the nearest 100
200
695 + 487 = N
N = 1,182
1,325 - 857 = N
N = 468
Maxwell has 719 cards in his collection. He gave 127 cards to his little brother. Then he bought 54 more cards from the store. How many cards does Maxwell now have?
Equation with a variable, solution with a label and be ready to explain your reasoning.
(719 - 127) + 54 = N or (719 + 54) - 27 = N
N = 646 cards
I know that to find the total number of cards he has now, I have to subtract the cards he gave away from the cards he started with then add the new cards he bought.
Melinda read that the aquarium had about 20 sharks in their new exhibit. She wanted to know the exact amount of sharks so she was going to count them during her visit. What are all the possible numbers of sharks that Melinda could count that would round to 20? Justify your answers.
15, 16,17, 18, 19, (20) 21, 22, 23, or24 would all round to 20.
Midpoints are 15 and 25. From the midpoint of 15 up to 24 would all round to 20.