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by j_shreyans » Mon Sep 08, 2014 10:11 pm
Adam and Brianna plan to install a new tile floor in a classroom. Adam works at a constant rate of 50 tiles per hour, and Brianna works at a constant rate of 55 tiles per hour. If the new floor consists of exactly 1400 tiles, how long will it take Adam and Brianna working together to complete the classroom floor?

A)26 hrs. 44 mins.
B)26 hrs. 40 mins.
C)13 hrs. 20 mins.
D)13 hrs. 18 mins.
E)12 hrs. 45 mins.

OAC

i was doing like below:

Adam 1 tile =1/50

Briana 1 tile =1/55

(Adam+Briana) 1 tile = 1/50+1/55 = 21/550

for 1400 tile = 1400*550/21

where i am wrong in this?
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Source: — Problem Solving |

by abhasjha » Mon Sep 08, 2014 10:18 pm
Adam in 1 hour = 50 tiles
brian in 1 hour = 55 tiles

so togther = 50+ 55 = 105 tiles .....

so to complete 1400 tiles = (1400 / 105) = 40/3 hours = 13 hours 20 minutes

Answer C
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by [email protected] » Mon Sep 08, 2014 11:54 pm
Hi j_shreyans,

Although this question is presented in a "style" that is similar to a Work Formula question, it's actually just a Rate question. Abhasjha points out how the rates can be combined into one big rate....

50 tiles per hour + 55 tiles per hour = 105 tiles per hour

You can now use the "Distance Formula" to answer this question....

D = R x T
1400 tiles = 105 tiles/hour x Time

1400/105 = Time

13 1/3 hours = T

Final Answer: C

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