The speed of a car increases by 2 km/hr after every one hour. If the distance travelling in the first one hour was 35 km. What was the total distance travelled in 12 hours?
Answer & explanation
Correct answer: option 2
We have,
Speed of car increases after every hour = 2 km/h
Distance travelled in 1st one hour = 35 km
Distance travelled in 2nd hour = 35 + 2 = 37 km
Distance travelled in 3rd hour = 37 + 2 = 39 km
∴ Distance travelled by car in every hour will be in Arithmetic Progression.
35, 37, 39… up to 12 terms
First term = a = 35, common difference = d = 37 – 35 = 2, number of terms = n = 12
We know that,
Sum of n terms of an Arithmetic Progression = n/2{2a + (n – 1)d}
∴ Total distance travelled in 12 hours = 12/2{2 × 35 + (12 – 1)2} = 6(70 + 22) = 6 × 92 = 552 km