Which strategy would not correctly solve this story problem?
Dora ran for 3 times as long as she walked. She walked for 10 minutes more than she rode her bike. She walked for 30 minutes. How many minutes did Dora exercise altogether?
A.
Draw a diagram. First draw 3 dots (each dot represents 10 minutes) for how many minutes she walked. Draw 2 dots to represent the 20 minutes she rode her bike. Draw 9 dots for the three times as many minutes spent running. Count the dots and multiply by 10.
B.
Work backward. She walked for 30 minutes, she walked for 10 minutes more than she rode her bike, so subtract 10 from 30. She ran 3 times as long as she walked so multiply by 3.
C.
Use logical reasoning. Dora walked for 30 minutes and ran for 3 times as long as she walked so she must have run for 90 minutes. Dora walked for 10 minutes more than she rode her bike, so subtract 10 from 30 to get 20. Then add 20 + 30 + 90 to figure out how many minutes Dora exercised.
D.
Translate into an equation.
(3 × 30) + (30 – 10) + 30 = m