The speed of a car increases by 2 km/hr after every one hour. If the distance travelled in the first hour was 35 km, what was the total distance travelled in 12 hours?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 552 km
The speed rises by 2 km/hr each hour, so the distance covered in each hour also rises by 2 km: 35, 37, 39, ... km. These 12 distances form an arithmetic progression with first term 35 and common difference 2, and the total is its sum.
\(S_n=\frac{n}{2}\left[2a+(n-1)d\right]\), with n = 12, a = 35, d = 2
\(S_{12}=6\times(70+22)=6\times92=552\) km