# Work rate problem

• Jul 8th 2013, 11:59 AM
usre123
Work rate problem
Mary wraps 5 parcels in 2 minutes while Kerry unwraps a parcel every ten minutes. If both work together how long will it take them to have 120 wrapped parcels ready?
A) 5 mins
B) 10 mins
C) 20 mins
D) 35 mins
E) 50 mins
• Jul 8th 2013, 12:14 PM
earboth
Re: Work rate problem
Quote:

Originally Posted by usre123
Mary wraps 5 parcels in 2 minutes while Kerry unwraps a parcel every ten minutes. If both work together how long will it take them to have 120 wrapped parcels ready?
A) 5 mins
B) 10 mins
C) 20 mins
D) 35 mins
E) 50 mins

Hello,

let x denote the number of minutes it takes to get the 120 Parcels.

You know that Mary wraps $\frac52 \frac{parcels}{min}$

and Kerry unwraps $\frac1{10} \frac{parcels}{min}$

That means the number of parcels is determined by:

$\frac52 \frac{parcels}{min} \cdot x \ min - \frac1{10} \frac{parcels}{min} \cdot x \ min = 120 \ parcels$

Solve for x.
• Jul 8th 2013, 06:53 PM
usre123
Re: Work rate problem
Hey, its ok, I got it. Thanks a lot. It was really easy. Mary does 5/2= 2.5 boxes/minute. Kerry unwraps 1/10= 0.1 per minute. So Mary - Kerry (since they're doing opposite things) is equal to 2.4. Now 2.4 * 120= 50 minutes.
• Jul 8th 2013, 11:03 PM
earboth
Re: Work rate problem
Quote:

Originally Posted by usre123
Hey, its ok, I got it. Thanks a lot. It was really easy. Mary does 5/2= 2.5 boxes/minute. Kerry unwraps 1/10= 0.1 per minute. So Mary - Kerry (since they're doing opposite things) is equal to 2.4. Now 2.4 * 120= 50 minutes.

Hello,

you obviously calculated correctly but wrote it the wrong way:

$x = \frac{120\ parcels}{2.4\ \frac{parcels}{min}}$