Question

Shelley spent 17 minutes washing dishes. She spent 38 minutes cleaning her room. Explain how you can use mental math to find how long Shelley spent on the two tasks.

Answer 1

17 + 38 your add both numbers. and you get 55

Answer 2

All you need to do is round up 17 and 38 to 20 and 40 in your head. Solve for that in your head and then subtract 5 from the sum.

20+40=60
60-5+55