Question

a bus stops at the corner of elm street and oak street every half hour between 9 a.m. and 3 p.m. and every 15 minutes between 3 p.m. and 6 p.m. How many times will a bus stop at the corner between 9 a.m. and 6 p.m.

Answer 1

From 9 a.m to 3 p.m its 6hrs
$6 \times 2 = 12$
From 3pm to 6pm is 3 hours
$3 \times 4 = 12$
Answer is 24