Question

Yuki's guppies have begun to have babies. She started with 5 guppies. One week later, Yuki counted twice as many guppies in the fish tank. Each week afterwards, the number of guppies doubled. In how many weeks did Yuki have 160 guppies?

Answer 1

Week 1 = 5 guppies.
week 2 = 5x 2 = 10 guppies
week 3 = 10 x 2 = 20 guppies
week 4= 20 x 2 = 40 guppies
week 5 = 40 x 2 = 80 guppies
week 6= 80 x 2 = 160 guppies
Yuki had 160 guppies in 6 weeks.