**EXERCISE 7 (B)**

Question 1

**What percent of a day is the time duration of 3 hours?**

Sol :

Total hours in a day = 24 hours

Given hours = 3 hours in percentage

Hence , of a day represent 3 hours

Question 2

**About 67% of a human body’s total weight is water.If Aparna weights 70 kg, how much of her weight is water?**

Sol :

According to question:

67% of 70 kg

= 46.90 kg

Hence , 46.90 kg is water from 70 kg of total body weight

Question 3

**A person’s salary increases from ₹ 7,200 to ₹ 8,100.What is the percentage increase in his salary?**

Sol :

According to question:

Increase in salary = 8100 – 7200 = 900

Percentage increase

is the percentage increase in his salary

Question 4

**A fruit seller had some apples.He sells 40% apples and still has 420 apples.How many apples did he originally have?**

Sol :

Let the total number of apples is x

As , already mentioned 40% already sold which means 60% of total apples is equal to 420

⇒

⇒

⇒x=700

Hence , the total number of apples is 700

Question 5

**A water pipe is cut into pieces.The longer piece is 70% of the length of the pipe.By how much percent is the longer piece longer than the shorter piece?**

Sol :

Let the water pipe’s original total length be 100 m

Then Length of longer piece of pipe is 70% of original = 70 m

And Length of shorter piece of pipe is 30% of original = 30 m

As you can see here Longer piece is long by 70 – 30 = 40 m than shorter piece

In percentage the longer piece longer than the shorter piece

Question 6

**If a number is increased by 20% and the resulting number is again increased by 20%, what percent is the total increase?**

Sol :

Let the original number be 100 and Increased by 20%

Which is = 100 + 20% of 100

= 120

And again 20% increased

= 120 + 20% of 120

= 120 + 24

= 144

Total increase = 144 – 100 = 44

Percentage increase

= 44 %

Question 7

**If A’s income is 50% less than that of B, then B’s income is what percent more than that of A?**

Sol :

Let the income of B is 100

Then , A.T.Q A’s income is

A = B – 50% of B

= 100 – 50

A = 50

Difference in B’s income and A’s income = 100 – 50 = 50

Percentage increase in B’s income as compare to A’s income

= 100 %

Question 8

**If the price of petrol be raised by 20%, then what is the percentage by which a car owner must reduce its consumption so as not to increase his expenditure on petrol?**

Sol :

Let the original price of petrol is 100

New price = 100 + 20% of 100

= 120

Difference between prices = 120 – 100 = 20

Percentage decrease of use of petrol

Hence , the should reduce its consumption by

Question 9

**In an examination, 1100 boys and 900 girls appeared. 50% of the boys and 40% of the girls passed the examination.What is the percentage of candidates who failed?**

Sol :

Failed in boys = 50% of 1100 = 50×11 = 550

Failed in girls = 60% of 900 = 60×9 = 540

Total percentage of failed students

= 54.5%

**Question 10**

**A candidate who scores 30% fails by 5 marks, while another candidate who scores 40% marks get 10 more than minimum pass marks.What are the minimum pass marks required to pass?**

Sol :

Let x be the total marks . According to question

30% of x + 5 = minimum passing marks ..(i)

Also , minimum passing marks also equal to 40% of x – 10 ..(ii)

From (i) and (ii) , we get

⇒30% of x + 5 = 40% of x – 10

⇒+5+10=40% of x – 30% of x

⇒

⇒

⇒1500=10x

⇒

Total marks = x = 150 And

Minimum passing marks is equal to 30% of x + 5 [from(i)]

= 3×15 + 5

= 45 + 5

= 50

Hence , minimum passing marks is equal to 50

Question 11

**Out of his income, Mr.Raj spends 20% on house rents and 70% of the rest on household expenditure.If he saves ₹ 3,600 per month, then what is his total income per month?**

Sol :

Let the total income be x

A.T.Q

Spending on house = 20% of x

Remaining = Total income – spending on house

..(i)

Spending on households = 70% of remaining [from (i)]

Remaining = remaining [from(i)] – spending on households

And this remaining must be equal to his savings

⇒

⇒

⇒x=15000

Hence , total income is equal to 15000