# Math Help - SAT question.

1. ## SAT question.

This is a question taking from the SAT Question Of the Day.

A mechanic can install carburetors in 3 cars every 4 hours. At that rate, how long will it take the mechanic to install carburetors in 5 cars?

How can I do this. By the way tomorrow Is my SAT and I know I will do very poorly.

( Sorry if I posted this in the wrong section I din't know where is it suppose to go"

2. Originally Posted by vaironxxrd
This is a question taking from the SAT Question Of the Day.

A mechanic can install carburetors in 3 cars every 4 hours. At that rate, how long will it take the mechanic to install carburetors in 5 cars?

How can I do this. By the way tomorrow Is my SAT and I know I will do very poorly.

( Sorry if I posted this in the wrong section I din't know where is it suppose to go"
1 car done in 4/3 hours. Therefore ....

3. Originally Posted by mr fantastic
1 car done in 4/3 hours. Therefore ....
i said 3/4 = 5/x and I get 3x=4*5=20 therefore 20/3=6.66

4. It will help on these tests just to write out that math in words sometimes, if you can think better that way.

$\frac{1(mechanic) "fixes"3 (cars)}{"every"4(hours)}$

$\frac{1(mechanic)3(cars)}{4(hours)}= \frac{1(mechanic)5(cars)}{x(hours)}$

$\frac{3(cars)}{4(hours)}= \frac{5(cars)}{x(hours)}$

and you know how to solve that math! Good luck on your SAT you'll do real well.

5. A mechanic can install carburetors in 3 cars every 4 hours. At that rate, how long will it take the mechanic to install carburetors in 5 cars？
one way to do this is to find out the rate
rate=3/4per hours
then assume x= how long will it take the mechanic to install carburetors in 5 cars
3x/4=5
x=20/3
so the answer is 6+2/3 hours

6. Originally Posted by vaironxxrd
i said 3/4 = 5/x and I get 3x=4*5=20 therefore 20/3=6.66
Yes. But surely it is obvious from my previous post that the answer is got simply by multiplying 4/3 by 5 ....!

7. Remember:
a in b
c in ?

? = b/a * c

8. The amount of cars repaired is directly proportional to the time given, so:

3 cars : 4 hrs = 5 cars : x hrs

And by simple multiplication, and by rearranging the equation you get:

$x = \frac{20}{3}$,

which amounts to 6 hours 40 minutes.