1998 CEMC Gauss (Grade 7) Problems/Problem 12

Problem

Steve plants ten trees every three minutes. If he continues planting at the same rate, how long will it take him to plant 2500 trees?

$\text{(A)}\ 1 \dfrac{1}{4} \text{h} \qquad \text{(B)}\ 3 \text{h} \qquad \text{(C)}\ 5 \text{h} \qquad \text{(D)}\ 10 \text{h} \qquad \text{(E)}\ 12 \dfrac{1}{2} \text{h}$

Solution

Steve plants 10 trees every 3 minutes, meaning he plants one tree every $\frac{3}{10}$ minute.

To plant 2500 trees, he needs $\frac{3}{10} \cdot 2500 = 750$ minutes or $\frac{750}{60} = 12\dfrac{1}{2}$ hours.

The answer is $\text{(E)}.$

-edited by coolmath34

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1998 CEMC Gauss (Grade 7) Problems/Problem 12

Problem

Solution