Level 3
In a jar, the ratio of the number of yellow balls to the number of purple balls was 1 : 3. Each time, 5 yellow and 7 purple balls were taken out of the jar. A while later, only 120 purple balls were left in the jar. What was the total number of balls in the jar at first?
Level 2
Lance exercised for a total of (8f + 90) min in a week. For the first 3 days, he exercised for 2f minutes per day. For the next 2 days, he exercised for 30 minutes per day. For how long did he exercise for the rest of the week?
Level 3
It takes Faucet A 30 minutes to fill a tank measuring 12 cm by 10 cm by 22 cm completely while it takes Faucet B only 25 minutes. How long will it take to completely fill the tank with water if both the faucets are turned on at the same time? Leave the answer in minutes and round off to 2 decimal places.
