Answer: it will take a combined rate of 2.67 hours
Step-by-step explanation:
Father can do the job on the farm in 6 hours. This means that the father's unit rate of working will be 1/6
The older son can do it in 8 hours. This means that the older son's rate of working will be 1/8
The younger son can do same job in 12 hours. This means that the younger son's working rate is 1/12
When they work together, they will be working simultaneously. It means that their unit rates are additive. The combined unit rates will be
1/6 + 1/8 + 1/12 = (20 + 15 + 10)/120
45/120
Assuming it takes t hours for them to complete the work while doing it together. Their combined unit rate will be 1/t
45/120 = 1/t
45t = 120
t = 120/45 = 2.67 hours
Answer:
-1
Step-by-step explanation:
-7/10+7/15+1/-20+-9/10+11/15+11/-20
= -7/10 + -9/10 + 7/15 + 11/15 + 1/-20 + 11/-20
= -16/10 + 18/15 + 12/-20
= -8/5 + 6/5 + -3/5
= (-8+6-3)/5
= -5/5
= -1
To find a percentage of a number we multiply the percentage times the number and get the result, here we have the percentage and the result and need to find out which number it corresponds to, lets write an equation to do so and keep in mind that the percentage itself can be written in a different way:
225% = 225 out of 100 = 225/100
So we have this equation, where we call x the number we are looking for:
<span>(225%)(x) = 81
</span>(225/100)(x) = 81
so we solve for x:
225x = 81*100 = 8100
x = 8100/225
x = 36
The original number is 36, hence 225% of 36 is 81