# Please help me with the following questions: 1) 25% of 90 is what number? 2) 7% of 80 is what number? 3) What percent 38 is 3.8? 4) 70.6 is what percent of 635.4? Please help me solve these four...

Please help me with the following questions:

1) 25% of 90 is what number?

2) 7% of 80 is what number?

3) What percent 38 is 3.8?

4) 70.6 is what percent of 635.4?

Please help me solve these four problems.

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25% of 90 is what number? .25 times 90 equals **22.5**

7% of 80 is what number? .07(80) = **5.6**

N% of 3.8 is 38? n%(3.8) = 38; n= 38 divided by 3.8 ; **n = 10%**

70.6 is what percent of 635.4; 70.6= n%(635.4)

70.6 divided by 635.4 = n% ; **n = 11.11%** repeating 1

**1) 25% of 90 is what number?**

let x b the number,

hence, x=25% of 90

x=25% * 90

x= 25/100 * 90

x= .25*90

*x= 22.5*

**2) 7% of 80 is what number?**

let x be the number,

hence, x= 7% of 80

x=7% * 80

x= 7/100 * 80

x= 0.07 * 80

*x= 5.6*

**3) What percent 38 is 3.8?**

let x be the percent,

x% of 38 = 3.8

x% * 38 = 3.8

x% = 3.8/38

x% = 0.1

x/100 = 0.1

x= 0.1*100

*x= 10%*

**4) 70.6 is what percent of 635.4?**

let x be the percent:

x% of 635.4 = 70.6

x/100 * 635.4 =70.6

x/100 = 70.6/635.4

x/100 = 0.111

x= 100*0.111

*x= 11%*

1) 90 x .25 = 22.5

2) 80 x .07 = 5.6

3) 38 / 3.8 = 10 so 10%

4) ( 70.6 / 635.4 ) x 100 = 11%

1. 25% of 90 To solve this, turn 25% into a fraction. After it is a fraction, multiply it by 90 to find 25% of 90. 90 x .25 = 22.5

2. 7% of 80 Same as the first question, turn the percent into a fraction and multiply them. 80 x .07 = 5.6

3. percent 38 is 3.8 Divide 38 by 3.8 to find out what percent. 38 / 3.8 = 10%

4. 70.6 is what percent of 635.4 First write the equation down as a cross multiplication problem. 70.6 / 635.4 = ? / 100 . Then multiply 70.6 and 100. After you have done all that, then divide the product by 635.4. 7060 / 635.4 = 11.1%

1) 25% of 90 is what number? 90 x .25 = **22.5**

2) 7% of 80 is what number? 80 x .07 = **5.6**

3) What percent 38 is 3.8? 38 / 3.8 = 10 so** 10%**

4) 70.6 is what percent of 635.4? ( 70.6 / 635.4 ) x 100 = **11%**

1) 25% of 90= 25/100 * 90

= 1/4 *90

=** 22.5**

2) 7% of 80= 7/100*80=** 5.6**

3) 38/3.8 = **10%**

4) 70.6/635,4 * 100= **11.1% **( to three sig. fig.)

Follow these simple steps for each question.

**Q1. 25% of 90 is what number?**

i) Express 25% as: % (25/100); fraction (¼, when simplified by dividing through with 25); or decimal (0.25, when you divide 25 by 100 or get the inverse of ¼)

ii) Now, you can multiply 90 by any three expressions - 25/100, ¼, 0.25 - to calculate your answer. They should give the same result. Let's check!

25/100 x 90 = 25/100 x 90/1

= (25 x 90)/(100 x 1)

= 2250/100

= 22.5

¼ x 90 = (1 x 90)/(4 x 1)

= 90/4

= 22.5

or,

0.4 x 90 = 22.5

**Q2. 7% of 80 is what number?**

Follow the same steps above and you get: 7/100 or 0.07. Now use (multiply) either 7/100 x 80, or 0.07 x 80 to calculate your answer. Let's calculate then,

7/100 x 80 = 7/100 x 80/1

= (7 x 80)/(100 x 1)

= 560/100

= 5.6

or,

0.07 x 80 = 5.6

**Q3. What percent of 3.8 is 38?**

i) Define your unknown (%), say x*, *as an equation.

So your equation becomes: 3.8*x* = 38.

ii) Now solve for *x*

3.8*x* = 38

Isolate *x*, so

(3.8/3.8)*x* = 38/3.8

*x* = 10* *

**Answer: 10%**

iii) Check answer: Substitute *x* = 10 into the equation: 3.8*x* = 38, so

3.8*x* = 38, where *x* = 10

3.8(10) = 38

38 = 38

LHS = RHS so answer is correct!

**Q4. 70.6 of what % of 635.4?**

i) Apply the same rules as in Q3, so your equation becomes: 70.6*x* = 635.4

ii) Now solve for *x*

70.6*x* = 635.4

Isolate *x*, so

(70.6/70.6)*x* = 635.4/70.6

*x* = 9* *

**Answer: 9%**

iii) Check answer: Substitute *x* = 9 into the equation: 635.4*x* = 70.6, so

635.4*x* = 70.6, where *x* = 9

70.6(9) = 635.4

635.4 = 635.4

LHS = RHS so answer is correct!

1) .25*90=x

the number is 22.50

2) .07*80 =x

the number is 5.60

3)x/100*3.8=38

3.8x=3800

the percent is 1000%

4)70.6*x/100=635.4

70.6x=63540

the percent is 900%