Question : 30 is what percent of 40? Or, What percent of 40 is equal to 30?
Correct Answer 75%
Solution & Explanation
Solution
Given number = 40
To find, 30 is what percent of 40?
This question can be written as also
What percent of 40 is equal to 30?
⇒ ?% of 40 = 30
Let ? = m
And the meaning of "of" in mathematics is "Multiplication".
∴ m% of 40 = 30
⇒ m% × 40 = 30
⇒ m/100 × 40 = 30
⇒ 40 m/100 = 30
After cross multiplication, we get
40 m = 30 × 100
After transposing 40 to RHS, we get
m = 30 × 100/40
⇒ m = 3000/40
⇒ m = 75%
Thus, 75% of 40 = 30
Thus, Answer = 75%
Shortcut Method to find a number is what percent of other
If we have to find
? % of a = b
Here, let ? = m
Thus, above expression can be written as
m% of a = b
⇒ m/100 × a = b
⇒ m × a/100 = b
After cross multiplication, we get
m × a = b × 100
⇒ m = b × 100/a
Thus, using this formula, we can find a number (a) is what (m) percent of b
In the question, we have to find what percent of 40 = 30
Here, we have ? = m
a = 40
And, b = 30
Thus, using formula
⇒ m = 30 × 100/40
= 30 × 100/40
= 3000/40 = 75%
Thus, 75% of 40 = 30
Thus, 75% Answer
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