Solution

Since, the speed of the bike increases by 4 km/hr after every 1 hour, therefore the bike will travel 4 km extra after every 1 hour. Therefore, distance travelled by the bike in 1st hour = 16 km Distance travelled by the bike in 2nd hour = 16 + 4 = 20 km Distance travelled by the bike in 3rd hour = 20 + 4 = 24 km This form an AP i.e. 16, 20, 24………distance travelled in 18th hour Therefore, total distance travelled by the bike in 18 hours = sum of the AP Distance travelled in 18 hours = (n/2){2a + (n – 1)d} Where n = number of terms = 18, a = 1st term = 16 and d = common difference = 4 Therefore, distance travelled in 18 hours = (18/2){2 × 16 + (18 – 1) × 4} = (18/2)(32 + 68) = 900 km