Question

Amanda works as a carpenter and as a blacksmith.
She earns $\$20$ per hour as a carpenter and $\$25$ dollar per hour as a blacksmith. Last week, Giselle worked both jobs for a total of 30 hours, and earned a total of $\$690$dollar. How long did Giselle work as a carpenter last week, and how long did she work as a blacksmith?

• A. Carpenter : 15 hrs ; Blacksmith : 15hrs
• B. Carpenter : 19 hrs ; Blacksmith : 11hrs
• C. Carpenter : 12 hrs ; Blacksmith : 18hrs
• D. Carpenter : 10 hrs ; Blacksmith : 20 hrs

Answer 1

The correct option is C Carpenter : 12 hrs ; Blacksmith : 18hrs

Let 'c' be the number of hours she worked as a carpenter and 'b' be the number hours she worked as a blacksmith. Therefore the total number of hours worked $\Rightarrow$ c+b = 30.... (Eq. 1)
The total amount she earned = 20c + 25b = 690...(Eq.2).
Now, from Eq1, c = 30-b. Substitute this value of c in Eq.2 and solve for b. $\therefore$ b= 18;
20(30-b) + 25b = 690
$\Rightarrow$ 600 - 20b + 25b = 690
$\Rightarrow$ 5b = 90
$\Rightarrow$ b = 18
Use this value of b in Eq 1 and get c = 12
The correct option is C