Question

Select the correct answer. Joshua likes to read. He read 6 books when he was 6 years old. Every year he doubled the number of books he read the previous year. How many total books did he read between the ages of 6 and 10?
A. 60
B. 90
C.186
D.187

Answer 1

Answer: C.186

Step-by-step explanation:

1. You know that he read 6 books when he was 6 years old and every year he doubled the number of books he read the previous year.

2. Let's call $n$ the number of book he read each year and $n_t$ the number of books he read between the ages of 6 and 10, then:

 - At 6 years old:

$n=6$

- At 7 years old:

$n=6*2=12$

- At 8 years old:

$n=12*2=24$

- At 9 years old:

$n=24*2=48$

- At 10 years old:

$n=96$

The total books he read between the ages of 6 and 10 is:

$n_t=6+12+24+48+96\\n_t=186$