Digging a canal

https://www.facebook.com/video/video.php ... 0470751740

watch this video and try for yourself

as you said you have trouble with this kinds of problem i think the video will help you learn a nice method.

g2g no time to try to solve this

btw the other videos in this group are also quite nice.

mdavis wrote:Could someone explain how to tackle this problem step by step? I keep missing these types of problems and don't know what I am doing wrong. Thanks!

160 men can dig 3200 m of a canal in 12 days. How many men are required to dig 3600 m more of canal in 8 days?

A) 213
B) 144
C) 270
D) 225
E) 175

so we can make it simple like this
160 men dig 3200 so
1 men dig 3200/160=20 m in 12 days
so in one day one man dig 20/12 m so
suppose x men are required to dig 3600m in one day
x=3600/ 20/12=3600*12/20=180*12 =2160
so for 8 day
2160/8=270
so c is coreect answ

farmanetawah wrote: so we can make it simple like this
160 men dig 3200 so
1 men dig 3200/160=20 m in 12 days
so in one day one man dig 20/12 m so
suppose x men are required to dig 3600m in one day
x=3600/ 20/12=3600*12/20=180*12 =2160
so for 8 day
2160/8=270
so c is coreect answ

I like to look at it this way also because once you get the rate per person per day (or per machine per hour or per 1 worker per 1 time period) then you can take that anywhere.

With the above example you can also take a sec to reduce the fractions so the math is a bit easier.

20/12 = 5/3
rate = 5/3, we know the time = 8 days so 8*5/3 = 40/3
so 40/3 * x = 3600
x = 3600 * 3/40
x = 90 * 3 = 270

Answer = C

-Carrie

Thanks so much for the help!