21. If the side of a square increases by 21% then its area gets increased by:

यदि किसी वर्ग की भुजा में 21% की वृद्धि होती है तो उसके क्षेत्रफल में कितनी वृद्धि होगी:

Option “D” is correct.

Given data:

Percentage increase in side of square = 21%

Concept used:

Increased quantity by x% = Initial quantity × [(100 + x%)/100]

Area of square = (side)2

% change = [(final quantity – initial quantity)/initial quantity] × 100

Calculation:

Let length of side (s) be 100 unit.

Area of square (A) = (side)2

⇒ 1002

⇒ 10000 unit2

Increased side (s2) = 100 × [(100 + 21)/100]

⇒ 100 × 121/100

⇒ 121 unit

Area of new square (A2) = (s2)2

⇒ 14641 unit2

% change = [(A2 – A1)/A1] × 100

⇒ [(14641 – 10000)/10000] × 100

⇒ (4641/10000) × 100

⇒ 46.41%

∴ Area of square will be increased by 46.41%.

Alternate Method

Concept used:

% increased by x and y

Overall % increase = x + y + xy/100

Calculation:

Area of square = (side)2 = side × side

∴ Increase in side will reflect as dual increase in area.

% increase = 21%

⇒ Overall % increase = 21 + 21 + (21 × 21)/100

⇒ 42 + 441/100

⇒ 42 + 4.41

⇒ 46.41%

∴ Area of square will be increased by 46.41%.

22. In a class test, a student must secure 30% marks to pass. Amit gets 225 marks, but fails by 15 marks. What are the maximum marks for the test?

किसी कक्षा की परीक्षा में, एक छात्र को उत्तीर्ण होने के लिए 30% अंक प्राप्त करने चाहिए। अमित 225 अंक प्राप्त करता हैं, लेकिन वह 15 अंकों से अनुत्तीर्ण हो जाता है। परीक्षा के अधिकतम अंक क्या है?


Option “B” is correct.

Given:

Passing marks percentage = 30%

Marks obtained by the student = 225

Fails by marks = 15

Concept used:

Maximum marks percentage = 100%

Calculation:

Amit gets 225 marks and fails by 15 marks

⇒ Pass marks = 225 + 15

⇒ 240 Marks

Now, according to question, percentage marks need to pass = 30%

⇒ 30% = 240 Marks

⇒ 100% = (240/30) × 100 Marks

⇒ 800 Marks

∴ Required Maximum marks = 800

23. If 15% of Amit’s income is the same as 20% of Rohit’s income. What is the Ratio of their income?

यदि अमित की 15% आय रोहित की आय के 20% के बराबर है। उनकी आय का अनुपात क्या है?


Option “C” is correct.

Calculation:

Let the income of Amit be Rs. x

Let The income of Rohit be Rs. y

According to the question,

15% of x = 20% of y

⇒ (15/100) × x = (20/100) × y

⇒ x/y = 20/15

⇒ x/y = 4/3

 The ratio of their income is 4  3.  

24. 0.06% of 250% of 1600 is _________.

 1600 के 250% का 0.06% _________ है।


Option “D” is correct.
0.06% of 250% of 1600 = (0.06 × 250 × 1600)/(100 × 100) = 24000/10000 = 2.4

25. If 50% of a number is added to 75, then the result is the number itself. The number is:

यदि एक संख्या का 50% भाग 75 में जोड़ दिया जाता है, तब प्राप्त परिणाम स्वयं संख्या होती है। वह संख्या है:


Option “A” is correct.

Let the number be x.

50% of x + 75 = x

⇒ 50/100 × x + 75 = x

⇒ 50x + 75 × 100 = 100x

⇒ 7500 = 50x

⇒ x = 150

26. The price of sugar is increased by 20%. A person wants to increase his expenditure by 8% only. By what percent should he decrease his consumption?

चीनी की कीमत में 20% की वृद्धि हुई है। एक व्यक्ति अपने खर्च में केवल 8% की वृद्धि करना चाहता है। तो उसे अपनी खपत में कितने प्रतिशत की कमी करनी चाहिए? 

Option “B” is correct.

Let the initial price of sugar be 100x.

Price of sugar after increased = 100x × [120/100] = 120x

Person wants his expenditure increase by 8% only, so his expenditure should be = 100x × [108/100] = 108x

∴ Required percentage = (120x – 108x)/120 × 100 = 10%

27. In an examination, 53% of the candidates failed in science and 48% failed in mathematics. If 40% failed in both subjects, what percentage passed in both subjects?

एक परीक्षा में, 53% उम्मीदवार विज्ञान में अनुत्तीर्ण हुए हैं और 48% उम्मीदवार गणित में अनुत्तीर्ण हुए हैं। यदि 40% दोनों विषयों में अनुत्तीर्ण हुए हैं, तब दोनों विषयों में उत्तीर्ण कुल उम्मीदवारों का प्रतिशत क्या है?

Option “B” is correct.

Given,

Percentage of students failed in only Science = 53 – 40 = 13%

Percentage of students failed in only Mathematics = 48 – 40 = 8%

Percentage of students passed in both subjects

= 100 – 13 – 8 – 40 = 39%

28. The sum of the salaries of A and B is Rs. 42,000. A spends 75% of his salary and B spends 90% of his salary. Now their savings are the same. What is A’s salary (in Rs.)?

A और B के वेतन का योग 42,000 रुपये है। A अपने वेतन का 75% और B अपने वेतन का 90% खर्च करता है। अब उनकी बचत एक समान है। A का वेतन (रुपये में) कितना है?

.

Since their savings are same

∴ A × 25% = B × 10%

⇒ 5 A = 2 B

⇒ A/B = 2/5

Let the salaries of A and B be 2x and 5x respectively

∴ 2x + 5x = 42,000

⇒ 7x = 42,000

⇒ x = 6,000

∴ Salary of A = 2 × 6000 = Rs. 12000

29. Price of onions were increased by 25%. What percentage subsidy should the government provide on onions so that the effective price rise for consumers is only 10%?

प्याज की कीमत में 25% की वृद्धि की गई। सरकार को प्याज पर कितना प्रतिशत अनुदान देना चाहिए ताकि उपभोक्ताओं के लिए प्रभावी मूल्य वृद्धि केवल 10% हो?

Option “B” is correct.

⇒ Let the initial price of onions be Rs. 100

⇒ Price of onions after 25% rise = 100 + 100 × 25/100 = 125

⇒ Final price after government subsidy = 100 +10/100 × 100 = 110

⇒ Subsidy to be provided by government = 125 – 110 = 15

⇒ Subsidy in percentage = 15/125 × 100 = 12%

30. Represent 0.32 into percentage.

0.32 को प्रतिशत में बदलिए

Option “C” is correct.

∵ We know that, x/100 = x%

⇒ x = 100x%

Now, let’s put x = 0.32

⇒ 0.32 = 100 × 0.32%

⇒ 0.32 = 32%

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