2005 CEMC Gauss (Grade 7) Problems/Problem 20

Problem

While driving at $80 km/h$, Sally’s car passes a hydro pole every four seconds. Which of the following is closest to the distance between two neighbouring hydro poles?

$\text{(A)}\ 50 m \qquad \text{(B)}\ 60 m \qquad \text{(C)}\ 70 m \qquad \text{(D)}\ 80 m \qquad \text{(E)}\ 90 m$

Solution

Since Sally’s car travels $80 km/h$, it travels $80,000 m$ in one hour. Since there are $60$ minutes in an hour, the car travels $\frac{1}{60}\times 80,000 m$ in one minute. Since there are $60$ seconds in a minute, the car travels $\frac{1}{60}\times \frac{1}{60}\times 80,000 m$ in one second. Therefore, in $4$ seconds, the car travels $4\times \frac{1}{60}\times \frac{1}{60}\times 80,000 = 88.89 m$. Of the possible choices, this is closest to 90 m. Therefore, the answer is $E$.

See Also

2005 CEMC Gauss (Grade 7) (ProblemsAnswer KeyResources)
Preceded by
Problem 19
Followed by
Problem 21
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
CEMC Gauss (Grade 7)
Invalid username
Login to AoPS