Answer :
She reads 15.5 pages every 30 minutes. There are two 30 minutes in one hour (60 minutes) so the answer is 15.5*2 = 31.
Step 1: Find out how mnay pages she reads in an hour.
15.5 ~ 0.5 hour
(2)15.5 ~ (2) 0.5 hour
31 ~ 1 hour
Answer: d) 31 pages per hour
15.5 ~ 0.5 hour
(2)15.5 ~ (2) 0.5 hour
31 ~ 1 hour
Answer: d) 31 pages per hour