Lisa gives her little brother Sam a 15-second (sec) head start in a 300-meter (m) race. During the race. Sam runs at an average speed of 5 m/sec and Lisa runs at an average speed of 8 m/sec, not including the head start. Since the time Lisa started running, what is the best approximates the number of seconds that had passed when Lisa caught up to Sam?

A businessman agrees to pay a debt of Tk. 20,000 with 10% compound interest. After how many years he will pay total amount of Tk. 51,874.85.

In a factory, 60% workers like tea, and 30% workers like tea but not coffee. Find the number of workers:

Who like both the drinks?

In a factory, 60% workers like tea, and 30% workers like tea but not coffee. Find the number of workers:

Who like coffee but not tea assuming 100% workers like either tea or coffee?

In a class, if 4 students sit in each bench, 3 benches remain empty. But if 3 students sit in each bench, 6 students do not get any seat. Find the total number of students. 

The ratio of prices of two houses was 16:23. Two years later when the prices of the first had risen by 10% and that of second by Tk. 477, the ratio of their prices become 11:20. Find the original prices of the two houses.