Practice Net increase or decrease - quantitative aptitude Online Quiz (set-1) For All Competitive Exams
Q-1) The price of an edible oil is increased by 25%. To maintain the budget, Sushma reduces the consumption of this oil by 20%. The increase in expenditure due to this edible oil is:
(a)
(b)
(c)
(d)
Cost of edible oil = 100 per kg.
Consumption = 1 kg.
Again, New price = 125 per kg.
Consumption = 0.8 kg.
Expenditure = Rs.(125 × 0.8) = Rs.100
OR
Percentage effect = $(x + y + {xy}/100)%$
=$(25 - 20 - {25 × 20}/100)$% = 0%
Q-2) If the income tax is increased by 19%, the net income is reduced by 1%. The rate of income tax is
(a)
(b)
(c)
(d)
Let the income be Rs.x and the rate of income tax be y %
According to the question,
${xy × 1.19}/100 - {xy}/100 = (x - {xy}/100) × 1/100$
$1.19 xy - xy = x - {xy}/100$
$0.19 y = 1 - y/100$
$y/100 + 0.19y = 1 ⇒ ({1 + 19}/100) = 1$
$y = 100/20 = 5%$
Q-3) A number increased by 22$1/2$% gives 98. The number is
(a)
(b)
(c)
(d)
If the number be x, then $x × 245/200 = 98$
$x = {98 × 200}/245 = 80$
Q-4) A number is decreased by 10% and the resulting number is again decreased by 20%. What is the final percentage of decrease?
(a)
(b)
(c)
(d)
Effective percentage decrease
= $(x + y + {xy}/100)%$
= $(-10 - 20 + {(-10) × (-20)}/100)%$
= (-30 + 2)% = -28%
Q-5) A man spends 75% of his income. His income increases by 20% and his expenditure also increases by 10%. The percentage of increase in his savings is
(a)
(b)
(c)
(d)
Man's income = Rs.100 (let)
Expenditure = Rs.75
Savings = Rs.25
New income = ${100 × 120}/100 = Rs.120$
New expenditure = ${75 × 110}/100 = Rs.82.5$
Savings = 120 – 82.5 = Rs.37.5
Increase in savings = 37.5 – 25 = Rs.12.5
Increase per cent = $12.5/25 × 100 = 50%$
Q-6) The difference between the value of the number increased by 20% and the value of the number decreased by 25% is 36. Find the number.
(a)
(b)
(c)
(d)
Let the number be x.
(20 + 25)% of x = 36
${45x}/100 = 36$
$x = {36 × 100}/45$ = 80
Q-7) A number reduced by 25% becomes 225. What per cent should it be increased so that it becomes 375?
(a)
(b)
(c)
(d)
Clearly, 75% of the number = 225
Number = ${225 × 100}/75$ = 300
Again, 125% of 300 = 375
Hence, the number should be increased by 25%
Q-8) The sum of two numbers is 520. If the bigger number is decreased by 4% and the smaller number is increased by 12%, then the numbers obtained are equal. The smaller number is
(a)
(b)
(c)
(d)
Larger number = x and smaller number = 520 – x
${96x}/100 = {520 - x}/100 × 112$
96x = 520 × 112 – 112x
112x + 96x = 520 × 112
208x = 520 × 112
$x = {520 × 112}/208 = 280$
Smaller number = 520 – 280 = 240
Q-9) The number of employees working in a farm is increased by 25% and the wages per head are decreased by 25%. If it results in x % decrease in total wages, then the value of x is
(a)
(b)
(c)
(d)
Let the original number of employees be 100 and wages per head be Rs.100.
Total wages = Rs.(100 × 100) = Rs.10000
New number of employees = 125
New wages per head = Rs.75
Total new wages = Rs.(125 × 75) = Rs.9375
Decrease = Rs.(10000 – 9375) = Rs.625
Percentage decrease =$625/10000 × 100$
=$625/100 = 25/4%$
Q-10) The cost of an article worth Rs.100 is increased by 10% first and again increased by 10%. The total increase in rupees is
(a)
(b)
(c)
(d)
Using Rule 7,
Percentage effect = $(10 + 10 + {10 × 10}/100)$% = 21 %
Increase = Rs.21