Question

an important programme was to be broadcast from mumbai at 7:30 p.m. this was heard by some indian sailors near ivory coast in West Africa at 20 degree west longitude. what was the local time there?

Answer 1

The country of Ivory Coast is in West Africa which is at a distance of thousands of miles. In terms of time zones, the country is exactly 5 hours and 30 minutes  behind in time. E.g. if it's 5:30 am in India, it will be 12:00 am in Ivory coast.

For this question, since the program is being aired at 7:30pm from Mumbai, the Indian Sailors in Ivory coast can check it out at 2:00pm, Ivory coast time.
It is a simple calculation and I really hope this answers your question

Answer 2

The longitude of Mumbai is 73.E and of ivory coast is 20.w so first we will add the longitudes 73+20=93 and then multiply it with 4 as 1 longitude =4 min so 93×4=372 min or 6 hr 12 min as ivory coast is west of Mumbai we will subtract it from time of Mumbai 7:30-6:12=1:18 so time will be 1:18 pm

Hope it would help