# RRB NTPC Cbt Online Practice Bits Set - 21

**Quantity**

**1. The average age of four boys. five years ago was 9 years. On including a new boy, the present average age of all the ﬁve is 15 years. The present age of the new boy is**

(1) 14 years

(2) 6 years

(3) 15 years

(4) 19 years

**2. The cost of a piece of diamond varies with the square of its weight. A diamond of Rs. 5,184 value is cut into 3 pieces whose weights are in the ratio l : 2 : 3. Find the loss involved in the cutting.**

(1) Rs. 3,068

(2) Rs. 3,088

(3) Rs. 3.175

(4) Rs. 3,168

**3. A discount of 30% on the marked price of a toy reduces its selling price by Rs. 30. What is the new selling price (in Rs.)?**

(1) 70

(2) 21

(3) 130

(4) 100

**4. Pipe A alone can ﬁll a tank in 8 hours. Pipe B alone can fill it in 6 hours. If both the pipes are opened and after 2 hours pipe A is closed, then the other pipe will fill the tank in**

(1) 6 hours

(2) 3.5 hours

(3) 4 hours

(4) 2 .5 hours

**5. The population of a town is 15000. If the number of males increases by 8% and that of females by 10%, then the population would increase to 16300. Find the number of females in the town.**

(1) 4000

(2) 6000

(3) 3000

(4) 5000

**ANSWERS with Expiation:**

1. (4) Sum of the present ages of four boys =
9 * 4 + 20 = 56 years

Sum of the present ages of five boys = 15 * 5
= 75 years

so Present age of new boy = 75 – 56 = 19
years

2. (4) If the weight of a piece of diamond be 6 x units, then
Original price α(6x)^2 = 36kx^2

so 36.kx^2 = 5184 ………(i) Again, New price =
k(x^2 + 4x^2 + 9x^2)

= 14kx^2 = (14 * 5184)/36 = Rs. 2016 so Loss
= 5184 – 2016

= Rs. 3168

3. (1) 30% = Rs. 30 so 100% = Rs. 100

New S.P. = 100 -30 = Rs. 70

4. (4) Part of the tank filled by both pipes
in two hours

= 2 (1/8 + 1/6) = 2(3 + 4)/24 = 7/12 Remaining
part = 1 – 7/12 = 5/12

Time taken by B in filling the remaining part
= 5/12 * 6 = 5/2 = 2 1/2 hours

5. (4) If the number of females be x, then
number of males = 15000 – x so x * 10/100 + (15000 –x) * 8/100

= 16300 – 15000 = 10x + 120000 – 8x

= 1300 * 100 => 2x = 130000 – 120000 =
10000 =>x = 5000

**Reasoning**

**6.‘A’ man starts from a point and walks 2 km towards North, turns towards his right and walks 2 km, turns right again and walks. What is the direction now he is facing?**

(1) South

(2) South-East

(3) North

(4) West

**7. Kamu walks 5 kms straight from her house towards west then turns right and walks 3 kms. There-after she takes left turn and walks 2 km. further, she turns left and walks 3 km. Finally, she turns right and walks 3 kms. In what direction she is now from her house?**

(1) West

(2) North

(3) South

(4) East

**8. Amit travelled 15 kms. East-ward, then turned left and travelled 5 kms, then turned left and travelled 15 kms. Hose far was Amit from the starting point?**

(1) 30 kms.

(2) 35 kms.

(3) 15 kms.

(4) 5 kms.

**9. At 12.30 the hour hand of a clock faces North and the minute hand faces South. At 2.45 the minute had will be in which direction?**

(1) North-West

(2) West

(3) South-East

(4) East

**10. Mamatha walks 14 metres towards west, then turns to her right and walks 14 metres and then turns to her left and walks 10 metres. Again turning to her left she walks 14 metres. What is the shortest distance (in metres) between her starting point and her present position?**

(1) 38 m

(2) 28 m

(3) 24 m

(4) 10 m

**Answers:**

6.1

7.1

8.4

9.2

10.3

**General Knowledge**

1.The
casual organism of polio is?

A)
A
worm

B)
A
bacteria

C)
A
fungi

D)
A
virus

**Answer: D**

2. Which
of the following symbiotic associations forms a lichen?

A)
An
algae and a fungus

B)
An
algae and a bryophyte

C)
A
bacterium and a fungus

D)
A
bacterium and a gymnosperm

**Answer: A**

3. Whose
experiment proved that the speed of
light was always the same?

A)
Isobar

B)
Iso
electronic

C)
Isotopes

D)
Isotones

**Answer: C**

4.Radioactive
isotope of hydrogen is?

A)
Protium

B)
Deuter

C)
Tritium

D)
All

**Answer: C**

5.Which
one of the following is NOT a constituent of human development index(HDI) ?

A)
Per
capita income

B)
Life
expetancy at birth

C)
Gross
enrolment rate

D)
Health
and nutrition

**Answer: C**

6.Which
if the following is a cool current?

A)
Tides

B)
Waves

C)
Current

D)
Tsunami

**Answer: A**

7.The
tides are primarily caused by?

A)
Gravitational
forces of the moon

B)
Gravitational
force of the sun

C)
Gravitational
forces of the earth

D)
None
of these

**Answer: A**

8.National
agricultural insurance scheme replacing comprehensive crop insurance scheme was
introduced in the year?

A)
1997

B)
1998

C)
1999

D)
2000

**Answer: C**

9.The
caves and rock-cut temples at ellora are?

A)
Hindu
and buddhist

B)
Buddhist
and jain

C)
Hindu
and jain

D)
Hindu,
buddhist and jain

**Answer: D**

10.Which
article of indian constitution enumerates fundamental duties of indian
citizens?

A)
Article
50-A

B)
Article
50-b

C)
Article
51-A

D)
Article
51-B

**Answer: C**

RRB NTPC Cbt Online Practice Bits Set - 21
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