MATH QR practice

[keliao]

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If 20 men or 24 women or 40 boys can do a job in 12 days working for 8 hours a day, how many men working with 6 women and 2 boys take to do a job four times as big working for 5 hours a day for 12 days? (1)8 men (2)12 men (3)2 men (4)24 menand is 3) 2 men

Solution:

Amount of work done by 20 men = 24 men = 40 boys or 1 man = 1.2 woman = 2 boys.

The man hours required to complete the new job = 4 times the man hours required to complete the old job. (As the new job is 4 times as big as the old job)
Let ‘n’ be the number of men required.
20 * 12 * 8 = n * 5 * 12 * 4. n = 8.

8 men working will be able to complete the given job.

However, the problem states that 6 women and 2 boys are working on the job.
6 women =

= 5 men and 2 boys = 1 man. The equivalent of 5 + 1 = 6 men are already working.

Therefore, 2 men a required to work with 6 women and 2 boys to complete the job.

how did they get 5 men ????????????

 

[Streetwolf]

IDK why they write 6/12 but if 24 women = 20 men, then 6 women = 5 men. That's where they get it from.

Similarly, 40 boys = 20 men so 2 boys = 1 man.

What I don't get is how it takes only 8 men to do this new job compared to the original 20. Not only is it 4x the original job but they are working fewer hours overall. Sounds like they'd need MORE people working.