HolaMaven wrote:
Mary takes 15 minutes to eat a plate of french fries. Ann takes 30 minutes to eat a plate of french fries. If Mary and Ann decide to eat fries, from the plate, each for a minute alternatively starting with Mary, how long will it take them to finish the plate, if each eats the french fries at her respective rate?
a. 8 mins
b. 10 mins
c. 18 mins
d. 20 mins
e. 45 mins
Use 30 fries (or any reasonable multiple of 15 and 30) to find out how many fries per minute each person eats. 1 plate, P = 30 fries. Substitute 30 fries, F, for 1 plate, P.
Mary = \(\frac{1P}{15min}\) = \(\frac{30F}{15min}\). Reduce.
M's rate = \(\frac{2F}{1min}\)
A's rate: \(\frac{1}{30}\) = \(\frac{30F}{30min}\) = \(\frac{1F}{1min}\)
There are 30 fries. Mary eats two fries in one minute. Ann eats one fry in 1 minute. But they don't eat during the same minute.
First minute: Mary eats two fries
Next minute: Ann eats one fry
So after two minutes, they have eaten 3 fries. How long will it take them to eat 30 fries?
\(\frac{3F}{2 min} = \frac{30F}{X mins}\)
3x = 60
x = 20 minutes
Answer D
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59% (01:50) correct 
