Percentage, General Mathematics

Question: If `40%` of `40%` of x `= 40,` then x is :
A
`100`

B
`400`

C
`250`

D
`1000`

Note: `40/100 xx 40/100 xx x = 40 ⇒ x` `= (40 xx 100 xx 100)/(40 xx 40)` `= 250`
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Question: `√3.6% of 40 = ?`
A
`2.8`

B
`1.8`

C
`1.2`

D
None

Note: `√3.6% of 40` `= √(3.6)/100 xx 40` `= √144/100` `= 12/10` `= 1.2`
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Question: By how much percent is four-fifth of`70` lesser than five-seventh of`112 ?`
A
`42%`

B
`30%`

C
`24%`

D
`36%`

Note: `4/5 xx 70` `= 56 & 5/7 xx 112` `= 80` Decrease over`80 = (80 - 56)` `= 24` Decrease over`100 = (24/80 xx 100)%` `= 30%`
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Question: What will be`160%` of a number whose`200%` is `140 ?`
A
`200`

B
`160`

C
`140`

D
`112`

Note: Let`200% of x = 140.` Then,`200/100 xx x = 140` `or x = 70` Now,`160% of 70 = 160/100 xx 70` `= 112.`
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Question: If `75%` of a number is added to `75` the result is the number itself. Then the number is :
A
`400`

B
`300`

C
`60`

D
`50`

Note: `75% of x + 75` `= x ⇒ x - 75/100 x = 75` `:. x - (3)/(4) x = 75` `or x/4 = 75` `or x = 75 xx 4` `= 300`
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Question: Subtracting`40%` of a number from the number, we get the result as `30`. The number is :
A
`28`

B
`50`

C
`52`

D
`70`

Note: `x - 40%` of `x = 30 ⇒ x - (40)/(100) x` `= 30 ⇒ x - (2)/(5) x = 30` `:. (3x)/5 = 30` `or x = (30 xx 5/3)` `= 50.`
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Question: If three fifth of a number is `40` more than `40%` of the same number what is the number ?
A
`100`

B
`150`

C
`200`

D
`400`

Note: `(3)/(5) x - 40%` 0f` x - 40 ⇒ (3)/(5) x - (40)/(100) x` `= 40` `or (3)/(5) x - (2)/(5) x = 40` `or x/5 = 40` `or x = (40 xx 5)` `= 200.`
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Question: A number, on subtracting `15` from it, reduces to its `80%.` What is `40%` of that number ?
A
`60`

B
`45`

C
`30`

D
`90`

Note: `x - 15` `= (80)/(100) x ⇒ x - 15` `= (4)/(5) x ⇒ x - (4)/(5) x = 15` `:. x/5 = 15` `or x = (15 xx 5)` `= 75.` Now,`40%` of `75` `= (40/100 xx 75)` `= 30`
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Question: Calculation shows that an angle is `37 1°/2.` The size obtained by drawing and measurement is `36°`. The error percent is :
A
`1 1/2`

B
`3`

C
`4`

D
`4 1/6`

Note: Error on`37 1/2` `= (37 1/2 - 36)` `= 1 1/2`. :. Error on `75/2 = 3/2.` Error on`100 = (3/2 xx 2/75 xx 100)` `= 4%`
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Question: The population of a town has increased from `133575` to `138918`. The percent increase in population is
A
`2.5`

B
`3`

C
`3.5`

D
`4`

Note: Increase on` 133575` `= (138918 - 133575)` `= 5343` :. Increase on `100 = (5343/133575 xx 100)%` `= 4%`
1. Report

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Question: If `40%` of `40%` of x `= 40,` then x is :

Question: `√3.6% of 40 = ?`

Question: By how much percent is four-fifth of`70` lesser than five-seventh of`112 ?`

Question: What will be`160%` of a number whose`200%` is `140 ?`

Question: If `75%` of a number is added to `75` the result is the number itself. Then the number is :

Question: Subtracting`40%` of a number from the number, we get the result as `30`. The number is :

Question: If three fifth of a number is `40` more than `40%` of the same number what is the number ?

Question: A number, on subtracting `15` from it, reduces to its `80%.` What is `40%` of that number ?

Question: Calculation shows that an angle is `37 1°/2.` The size obtained by drawing and measurement is `36°`. The error percent is :

Question: The population of a town has increased from `133575` to `138918`. The percent increase in population is