BTGModeratorVI wrote: ↑

Tue Dec 15, 2020 7:04 am

A certain plumber charges $92 for each job completed in 4 hours or less and $23 per hour for each job completed in more than 4 hours. If it took the plumber a total of 7 hours to complete two separate jobs, what was the total amount charged by the plumber for the two jobs?

(1) The plumber charged $92 for one of the two jobs.
(2) The plumber charged $138 for one of the two jobs.

Answer: B
Source: official guide

Target question: What was the total amount charged by the plumber for the two jobs?

Given: $92 for each job completed in 4 hours or less. $23 per hour for each job completed in more than 4 hours. Total work time was 7 hours

Statement 1: The plumber charged $92 for one of the two jobs
This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several scenarios that satisfy statement 1. Here are two:
Case a: the plumber spent 1 hour on one job (and received $92) and spent 6 hours on the other job (at $23/hours). In this case, the TOTAL amount charged = $92 + (6)($23) = $230
Case b: the plumber spent 2 hours on one job (and received $92) and spent 5 hours on the other job (at $23/hours). In this case, the TOTAL amount charged = $92 + (5)($23) = $207
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, read my article: https://www.gmatprepnow.com/articles/dat ... lug-values

Statement 2: The plumber charged $138 for one of the two jobs.
This means the plumber MUST have spent more than 4 hours on this job
So, the rate charged is $23/hour
$138/23 = 6. So, the plumber spent 6 hours on this job (and received $138), which means he spent 1 hour on the other job (and received $92)
So, the TOTAL amount charged = $138 + $92 = $230
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: B

Cheers,
Brent