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100

Your friend finds 34.5 + 6.8 and gets a sum of 413. Without adding, explain how you know your friend’s answer is not correct.

  • Notice that 34.5 is a little more than 30, and 6.8 is a little less than 7.
  • If you roughly add 30 and 7, you get 37 (and since 34.5 is more than 30, and 6.8 is close to 7, the true total would be a bit over 37).
  • Therefore, it cannot be 413, which is way too large compared to our rough estimate in the 40s.
  • If the person wrote the numbers as 345 and 68 (ignoring the decimal points) and then added them, they would get 413.
100

431.6-17.8=?

413.8

100

You run across the length of the soccer field until you reach the middle (45.72 m) , and then run back. Then you run across the entire length of the field (91.44 m). How far do you run altogether?

  1. Running to the middle of the field: 45.72 m
  2. Running back to the starting point: 45.72 m
  3. Running across the entire length of the field: 91.44 m
  4. Total distance: 45.72+45.72+91.44=182.88 m

Thus, you run 182.88 meters in total.

100

A musician buys an electronic keyboard for $89.94 and 2 books of sheet music for $7.99 each. How much does she spend in all?

  1. Calculate the cost of the 2 books of sheet music: 2×7.99=15.98 dollars
  2. Add the cost of the keyboard and the sheet music: 89.94+15.98=105.92 dollars

The musician spends $105.92 in total.

200

You have 6.5 megabytes of storage space left on your tablet. You want to download two eBooks: Tale of the Monster, which is 3.8 megabytes, and In the Game, which is 2.5 megabytes. Do you have enough space to download both eBooks?

  • Add the sizes of the two eBooks: 3.8 MB+2.5 MB=6.3
  • Compare the total size (6.3 MB) with your available storage (6.5 MB).
    Since 6.3 MB≤6.5, you have enough space.
  • Therefore, you can successfully download both eBooks.
200

The world record for the longest dog tongue is 18.58 centimeters. The previous record was 11.43 centimeters. By how many centimeters was the record broken?

Subtract the old record from the new record:

18.58 cm−11.43 cm=7.15 cm

So, the record was broken by 7.15 centimeters.

200

You have $35.50. You buy a movie for $15.89 and music for $12.50. How much money do you have left?

  1. First, add the cost of the movie and the music: $15.89+$12.50=$28.39
  2. Subtract this total from the amount of money you have: $35.50−$28.39=$7.11

Therefore, you have $7.11 left after your purchases.

200

You have $28.49. You spend $14.95 at a bowling alley. You win $35.00 for setting the record score for your age group. How much money do you have now?

  1. Subtract the amount spent at the bowling alley from your initial amount: 28.49−14.95=13.54 dollars
  2. Add the prize money you won: 13.54+35.00=48.54 dollars

You now have $48.54.

300

A chef needs 3.75 pounds of fish for a dinner party. She catches a fish that is 2.50 pounds and another fish that is 1.75 pounds. Does she catch enough fish for her dinner party?

Yes, she does. The total weight of the two fish is 2.50+1.75=4.25, which is more than the 3.75 pounds she needs.

300

The average high summer temperature in Death Valley, California, is 46.7 degrees Celsius. The hottest temperature ever recorded is 56.7 degrees Celsius. How much greater is the hottest recorded temperature than the average high temperature?

Subtract the average high temperature from the hottest recorded temperature:

56.7−46.7=10.0

Thus, the hottest recorded temperature is 10∘C greater than the average high temperature.

300

Three pumpkins are catapulted at a contest. How much farther does Pumpkin C travel than Pumpkin A?

• Pumpkin A travels 0.61 mile.

• Pumpkin B travels 0.28 mile farther than Pumpkin A.

• Pumpkin B travels 0.06 mile farther than Pumpkin C.

  1. Find the distance Pumpkin B traveled: 0.61+0.28=0.89 miles

  2. Find the distance Pumpkin C traveled: 0.89−0.06=0.83 miles

  3. Find how much farther Pumpkin C traveled than Pumpkin A:

  4. 0.83−0.61=0.22 miles

Thus, Pumpkin C traveled 0.22 miles farther than Pumpkin A.

300

Newton wins a $50 gift card to a craft store. He uses the card to buy a scrapbook for $19.99 and a set of markers for $10.75. How much money is left on his gift card?

  1. Subtract the cost of the scrapbook from the gift card balance: 50.00−19.99=30.01
  2. Subtract the cost of the markers: 30.01−10.75=19.26
  3. Thus, Newton has $19.26 left on his gift card.
400

Your school’s long jump record is 5.51 meters. You jump 3.38 meters on your first attempt. Your second attempt is 1.56 meters longer than your first. Do you break your school’s record?

No, you do not break the record. Your second attempt is 3.38+1.56=4.94, which is less than the record of 5.51 meters.

400

An athlete’s fitness tracker reads 2.69 miles at noon. The 6.34 miles show on the athlete’s fitness tracker before going to sleep that night. How many miles were recorded after noon?

Subtract the mileage reading at noon from the reading before going to sleep:

6.34 miles−2.69 miles=3.65 miles

Hence, the fitness tracker recorded 3.65 miles after noon.

400

A German shepherd weighs 24.75 pounds less than the Bernese mountain dog, which weighs 103.33 pounds. A husky weighs 21.67 pounds less than the German shepherd. How much do the three dogs weigh in all?

  1. Find the weight of the German shepherd: 103.33−24.75=78.58 pounds

  2. Find the weight of the husky: 78.58−21.67=56.91 pounds

  3. Find the total weight of all three dogs: 103.33+78.58+56.91=238.82 pounds

Thus, the three dogs weigh 238.82 pounds in total.

400

Descartes uses a metal detector at a beach. He finds 3 quarters, 6 dimes, 2 nickels, and 5 pennies. He drops 1 quarter and 2 pennies into the water. Then he finds 4 more dimes. How much money does Descartes have now?

Total before losing any coins: 0.75+0.60+0.10+0.05=1.50

Subtract the value of the lost coins:

  • 1 quarter lost: −0.25
  • 2 pennies lost: −0.02
  • Total after losing coins: 1.50−0.25−0.02=1.23

  1. Add the value of 4 more dimes found:

    • 4 dimes: 4×0.10=0.40
    • Final total: 1.23+0.40=1.63

Thus, Descartes now has $1.63.

500

The melting point of aluminum is 660.32 degrees Celsius. The melting point of aluminum is 403.86 degrees Celsius cooler than the melting point of gold. What is the melting point of gold?

The melting point of gold is found by adding the difference to the melting point of aluminum:

660.32+403.86=1064.18

So, the melting point of gold is 1064.18∘C

500

The world record for the longest fingernails on a pair of female hands is 576.41 centimeters. The world record for the longest fingernails on a single hand is 909.60 centimeters. How much longer is the world record for the longest fingernails on a single hand than the world record for the longest fingernails on a pair of female hands?


Subtract the world record for the longest fingernails on a pair of female hands from the world record for the longest fingernails on a single hand:

909.60 cm−576.41 cm=333.19 cm

Thus, the record on a single hand is 333.19 centimeters longer.



500

Your friend launches a water balloon 136.33 yards. Your cousin launches a balloon 15.67 yards farther than your friend and 8.33 yards farther than you. How much farther do you launch a balloon than your friend?

  1. Your cousin's launch distance: 136.33+15.67=152.00 yards

  2. Your launch distance: 152.00−8.33=143.67 yards

  3. The difference between your launch and your friend's launch: 143.67−136.33=7.34 yards

Thus, you launch the balloon 7.34 yards farther than your friend.

500

Your science teacher pays for an ultraviolet light, a beaker, and a glowing liquid kit with five $5 bills. The ultraviolet light costs $13.29. The beaker costs $7.99. Your teacher's change is $0.77. What is the cost of the glowing liquid kit?

  1. Calculate the total amount your teacher paid: 5×5=25.00

  2. Subtract the cost of the ultraviolet light and the beaker from the total amount: 25.00−13.29−7.99=3.72

  3. Since your teacher received $0.77 in change, subtract that from the remaining balance: 3.72−0.77=2.95

Thus, the cost of the glowing liquid kit is $2.95.