To determine the number of hours it takes for sally to paint one house, we use relations from the problem statement above. We use the concept of rates and ratios. For Tom, he would take 10 hrs to finish one house. So, we assign his rate as 1/10. For Sally, she would take x hours to finish one house. So, we assign 1/x. When both of them works, it would take only 4 hours. So, we write the rate as 1/4. It should be that the sum of the individual rates is equal to the rate when both are working.
1/10 + 1/x = 1/4
Solve for x,
x = 6.67 hours
Answer:
-1 is the answer
Step-by-step explanation:
Answer:
BC is just 3d+7??
Step-by-step explanation:
Must be 16 and 21 because we can see
30 and 70 has 10 as factor
24 and 44 has 2 as factor
12 and 30 has 2 as factor and all those factors are greater than one
Answer:
There are (63) combinations. The notation means "six choose three". Out of six items (flavors) choose three.
(nk)=n!k!(n−k)!.
(63)=6!3!3!.
Think of it this way. There are 6 ways to choose a flavor. Once you choose, there are 5 ways to choose the next. After that, there are 4 flavors left. which is 6!/3!=6⋅5⋅4⋅3⋅2⋅13⋅2⋅1=6⋅5⋅4=120.
But, you could have chosen {chocolate,vanilla,strawberry} and you get the same combination as {vanilla, strawberry, chocolate} so we have to divide by 3!=3⋅2⋅1=6 to account for the order of choosing.
So the number of combinations of flavors is (63)=1206=20.
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