First you find 80% of 90. Set up the proportion:
80 X
—— = —-
100 90
I’m simplifying the 80/100 so it’ll be easier to solve:
4 X
— = —-
5 90
Then cross multiply:
4(90) = 5x
360 = 5x
x = 72
So 80% of 90 is 72. (Or you could have multiplied 90 by 0.8 as a shortcut). Now you find 15% of 72. You can either multiply 72 by 0.15 or set up the proportion like this:
15 X
—— = —-
100 72
Cross multiply and solve. You should get 10.8
It will take her 12 minutes to run a full mile
Let x be the amount of the solution containing 10% of the chemical. Then, the solution with 40% chemical becomes 10 - x. The equation for balancing the chemical content of the solution is,
0.10x + 0.40(10 - x) = 0.25(10)
The value of x is 5. Hence, the druggist should mix 5 ounces of each. There are 2.5 ounces of chemical in the final mixture.
3/24
I’m guessing cause you times 3 by 8 to get 24 which is the amount of possibilities
Let the number be x
(3/7) x = t
I can't think of anything useful to add to this. How about an example?
Let x = 49
(3/7) x = t
(3/7) * 49 = t seven will go into 49
3 * 49 = t
t = 147
