During a thunderstorm, the time, T seconds, between seeing lightning and hearing thunder is directly proportional to the distance, d kilometers, of the observer from the centre of the storm. Thunder is heard 6 seconds after the lightning is seen when a storm is 35km away.
a. Find a formula for T in terms of d
b. Calculate, correct to the nearest kilometre, the distance of a storm when thunder is heard 10seconds after the lightning.

Question

During a thunderstorm, the time, T seconds, between seeing lightning and hearing thunder is directly proportional to the distance, d kilometers, of the observer from the centre of the storm. Thunder is heard 6 seconds after the lightning is seen when a storm is 35km away.
a. Find a formula for T in terms of d
b. Calculate, correct to the nearest kilometre, the distance of a storm when thunder is heard 10seconds after the lightning.