70% of what number is 21 and how do you do it

Mathematics

2 answers:

tester [92]3 years ago

4 0

The answer is 30 because you put 21/x= 70/100
you cross multiply 100 and 21 you get 2100 and you divide it by 70 you should get 30 cause you take out one 0 from both numbers and end up with 210 divided by 7 then you get 30

Katen [24]3 years ago

3 0

70 % of unknown number = 21
We multiply the percentage by a variable and make it = to the given value.
70% of n = 21
Change percent to decimal
70% = $\frac{70}{100}$ = 0.7
0.7n = 21
divide either sides by 0.7 to isolate n

$\frac{0.7n}{0.7}$ = $\frac{21}{0.7}$
0.7 and 0.7 cancels out
n = 30

0.7 × 30 = 21
70 % of 30 is 21
An example has been attached below

% of a number = multiply % by number
value is the % of a number = divide % by value

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Factor out the coefficient of the variable 5/6s+2/3

DochEvi [55]

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5/6 ( )

so what's in the parenthesis? well, if we distribute in our mind, S would just have to be by itself for it to work out. so we have

5/6 ( s )

but what about 2/3? well, if we're multiplying everything on the inside by 5/6, how can be get it to cancel and leave 2/3 alone? we could divide 2/3 by 5/6, right?

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now, when we distribute our 5/6, we'll have just 2/3 at the end. now let's simplify that end term so it looks a little better. if we divide by a fracion, that's the same as multiplying by the flipped version, so let's do that.

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we can reduce 12/15 by dividing the top and bottom by three.

= 4/5

so our final answer would be:

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15 points!!! GEOMETRY help please!!<br> Questions attached!

dolphi86 [110]

3. Look at the picture.

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TRUE: 1; 2; 4

6.
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