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?

552 km

We have,

Speed of car increases after every hour = 2 km/h

Distance travelled in 1^st one hour = 35 km

Distance travelled in 2^nd hour = 35 + 2 = 37 km

Distance travelled in 3^rd 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