A climber climbs up the lower part of the wall at a rate of 1.2 ft/min. The upper part of the wall is...?

Question

A climber climbs up the lower part of the wall at a rate of 1.2 ft/min. The upper part of the wall is more difficult, and she climbs at 0.8 ft/min. She reaches the top of the wall in 51.5 min. How long did it take her to climb the lower part of the wall? At what height on the wall did her rate change?

A. She spent 20 min climbing the lower wall and at 28.4 ft her rate of climb changed.

B. She spent 22 min climbing the lower wall and at 26.4 ft her rate of climb changed.

C.She spent 18 min climbing the lower wall and at 29.4 ft her rate of climb changed.

D.She spent 26 min climbing the lower wall and at 28.4 ft her rate of climb changed.

Answer 1

You can't answer this question without knowing either the average rate of climb for the whole wall, or the height of the wall.

However:

Looking at the four choices, only choice B (26.4 ft at 1.2 ft/min for 22 min.) is consistent with the 1.2 ft/min rate of climb.