Previous years average questions of SSC exams

1

The average age of A and B is 20 years. If A is to be replaced by C, the average would be 19 years. The average age of C and A is 21 years. The ages of A, B and C in order (in years) are

» Explain it

Correct Option: C

A + B = 2 × 20 = 40 yr

B + C = 2 × 19 = 38 yr

C + A = 2 × 21 = 42 yr

On adding all three,

2 (A + B + C) = 40 + 38 + 42 = 120

⇒ A + B + C = 60

∴ A = (A + B + C) – (B + C) = 60 – 38 = 22 yr

Similarly,

B = (A + B) – A = 40 – 22 = 18 yr

C = (C + A) – A = 42 – 22 = 20 yr

Note: In this question we can save 4-5 seconds by not calculating the age of the third person as with only the respective ages of A and B we can confirm the correct answer out of the given options.

Hence, option C is correct.

1

A तथा B की औसत आयु 20 वर्ष है। यदि A को C से प्रतिस्थापित किया जाए, तो औसत 19 वर्ष होगा। C तथा A की औसत आयु 21 वर्ष है। A, B और C की आयु क्रम में (वर्षों में) कितनी है?

» Explain it

सही विकल्प : C

A + B = 2 × 20 = 40 yr

B + C = 2 × 19 = 38 yr

C + A = 2 × 21 = 42 yr

On adding all three,

2 (A + B + C) = 40 + 38 + 42 = 120

⇒ A + B + C = 60

∴ A = (A + B + C) – (B + C) = 60 – 38 = 22 yr

Similarly,

B = (A + B) – A = 40 – 22 = 18 yr

C = (C + A) – A = 42 – 22 = 20 yr

Note: In this question we can save 4-5 seconds by not calculating the age of the third person as with only the respective ages of A and B we can confirm the correct answer out of the given options.

Hence, option C is correct.

2

The mean high temperature of the first four days of a week is 25°C where as the mean the last four days is 25.5°C. If the man of the whole week is 25.2°C then the temperature of the 4th days is

» Explain it

Correct Option: D

To solve this question we can apply a short trick approach

Value of	(	n + 1	)	th	result =	(	n + 1	)	× (b + c) – n × a
		2					2

Where

n is the total number of term = 7 days

b is the average of first four terms = 25

c is the average of last four terms = 25.5

a is the average of whole terms = 25.2

By the short trick approach, we get

Value of	(	n + 1	)	th	result =	(	7 + 1	)	× (25 + 25.5) – 7 × 25.2
		2					2

=	(	8	)	× (50.5) – 176.4 ⇒ 202 – 176.4 = 25.6
		2

Traditional method:

Total average of first 4 days = 4 × 25 = 100

Total average of last 4 days = 4 × 25.5 = 102

Total average of 7 days = 7 × 25.2 = 176.4

Temperature 4th day's = 100 + 102 – 176.4 = 25.6

Hence, option D is corrrect.

2

सप्ताह के पहले चार दिनों का औसत उच्च तापमान 25 डिग्री सेल्सियस है, जबकि पिछले चार दिनों में औसत 25.5 डिग्री सेल्सियस है। यदि पूरे सप्ताह का आदमी 25.2°C है तो चौथे दिन का तापमान होगा

» Explain it

सही विकल्प : D

To solve this question we can apply a short trick approach

Value of	(	n + 1	)	th	result =	(	n + 1	)	× (b + c) – n × a
		2					2

Where

n is the total number of term = 7 days

b is the average of first four terms = 25

c is the average of last four terms = 25.5

a is the average of whole terms = 25.2

By the short trick approach, we get

Value of	(	n + 1	)	th	result =	(	7 + 1	)	× (25 + 25.5) – 7 × 25.2
		2					2

=	(	8	)	× (50.5) – 176.4 ⇒ 202 – 176.4 = 25.6
		2

Traditional method:

Total average of first 4 days = 4 × 25 = 100

Total average of last 4 days = 4 × 25.5 = 102

Total average of 7 days = 7 × 25.2 = 176.4

Temperature 4th day's = 100 + 102 – 176.4 = 25.6

Hence, option D is corrrect.

3

A shop of electronic goods is closed on Monday. The average sales per day for remaining six days of a week is Rs. 15640 and the average sale of Tuesday to Saturday is Rs. 14124. The sales on Sunday is

» Explain it

Correct Option: B

Total sales of 6 days = 6 × 15640 = 93840

Total sales Tuesday to Saturday = 5 × 14124 = 70620

Sunday's sale = 93840 – 70620 = 23220.

Hence, option B is correct.

3

इलेक्ट्रॉनिक सामान की एक दूकान सोमवार को बंद रहती है. सप्ताह के शेष छह दिनों के लिए प्रतिदिन की औसत बिक्री 15640 रुपये है और मंगलवार से शनिवार तक की औसत बिक्री 14124 रुपये है। रविवार को कितनी बिक्री होगी?

» Explain it

सही विकल्प : B

Total sales of 6 days = 6 × 15640 = 93840

Total sales Tuesday to Saturday = 5 × 14124 = 70620

Sunday's sale = 93840 – 70620 = 23220.

Hence, option B is correct.

4

Find the average of the following set of numbers

354, 281, 623, 518, 447, 702, 876

» Explain it

Correct Option: D

Average =	354 + 281 + 623 + 518 + 447 + 702 + 876
	7

=	3801	= 543
	7

Hence, option D is correct.

4

निम्नलिखित संख्याओं के समूह का औसत ज्ञात कीजिए

354, 281, 623, 518, 447, 702, 876

» Explain it

सही विकल्प : D

Average =	354 + 281 + 623 + 518 + 447 + 702 + 876
	7

=	3801	= 543
	7

Hence, option D is correct.

5

The average marks obtained by a student in 6 subjects is 88. On subsequent verification it was found that the marks obtained by him in a subject was wrongly copied as 86 instead of 68. The correct average of the marks obtained by him is

» Explain it

Correct Option: C

Total number of marks = 88 × 6 = 528

Now, 528 – 86 + 68 = 510

Required average =	510	= 85.
	6

Hence, option C is correct.

5

एक विद्यार्थी द्वारा 6 विषयों में प्राप्त औसत अंक 88 हैं। बाद में सत्यापन करने पर यह पाया गया कि एक विषय में उसके द्वारा प्राप्त अंक 68 के बजाय 86 के रूप में गलत तरीके से कॉपी किए गए थे। उसके द्वारा प्राप्त किए गए अंकों का सही औसत क्या होगा?

» Explain it

सही विकल्प : C

Total number of marks = 88 × 6 = 528

Now, 528 – 86 + 68 = 510