SOLUTION: Jack usually mows his lawn in 5 hours. Maria can mow the same yard in 3 hours. How long will it take for them to mow the lawn together?

Algebra ->  Equations -> SOLUTION: Jack usually mows his lawn in 5 hours. Maria can mow the same yard in 3 hours. How long will it take for them to mow the lawn together?      Log On


   

Question 511623: Jack usually mows his lawn in 5 hours. Maria can mow the same yard in 3 hours. How long will it take for them to mow the lawn together?
Found 2 solutions by stanbon, josmiceli:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Jack usually mows his lawn in 5 hours. Maria can mow the same yard in 3 hours. How long will it take for them to mow the lawn together?
---
Jack rate = 1/5 job/hr
Maria rate = 1/3 job/hr
---
Together rate = 1/x job/hr
----------------------
Equation:
rate + rate = together rate
1/5 + 1/3 = 1/x
---
Multiply thru by 15x
3x + 5x = 15
8x = 15
x = 15/8 = 1 7/8 hr = 1hr 52.5 minutes (time to do the job together)
============================================
Cheers,
Stan H.
==================

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let t = the time for them
to mow 1 lawn working together
Jack's rate of mowing:
( 1 lawn ) / ( 5 hours )
Maria's rate:
{ 1 lawn ) / ( 3 hours )
Add their rates of working:
+1%2F5+%2B+1%2F3+=+1%2Ft+
Multiply both sides by +13t+
+3t+%2B+5t+=+15+
+8t+=+15+
+t+=+15%2F8+
This is 1 hour + 7/8 of an hour
+%287%2F8%29%2A60+=+52.5+
It takes them 1 hr and 52.5 min