Charlie boils seven eggs for his breakfast. He puts the eggs into the pan one at a time, but waits one minute after putting one egg in before putting the next egg in. If he boils each egg for three minutes, how long does the whole operation take from the moment he puts the first egg in to the moment he takes the seventh egg out?

see explanation

step-by-step explanation:

since the sequence is geometric there is a common ratio r between consecutive terms, that is

r = 4 ÷ - 2 = - 2

r = - 8 ÷ 4 = - 2

r = 16 ÷ 8 = - 2

the next term - 13 must be incorrect as it should be - 32 for the sequence to be geometric.

the first 4 terms are therefore geometric with common ratio r = - 2