** 51) ______ is used as a fire extinguisher. **

(A) Carbon dioxide

(B) Oxygen

(C) Hydrogen

(D) Nitrogen

** 52) Isotopes are atoms of the same element with different numbers of: **

(A) electron

(B) proton

(C) neutron

(D) positron

** 53) The most reactive metal is: **

(A) Indium

(B) Francium

(C) Manganese

(D) Iridium

** 54) Which from the following is not a conductor? **

(A) Copper

(B) Silicon

(C) Graphite

(D) None of these

** 55) If x-y=6 ad x+y=16 Then? **

(A) x=5 and y=3

(B) x=8 and y=5

(C) x=10 and y=3

(D) x=11 and y=5

** 56) If A completes a particular work in 10 days, and B completes the same work in 15 days while working separately. Then how many days they will take in working together? **

(A) 6

(B) 5

(C) 7

(D) 8

** 57) |_4| + (-4) ^{1} + (-4)^{2}=? **

(A) 0

(B) 1

(C) 8

(D) 16

** 58) The price of sugar increases by 32%. A family reduces its consumption so that the expenditure of the sugar is up by 10% only. If the total consumption of sugar before the price rise was 10 kg per month, then the consumption of sugar per month at present (in kg) is: **

(A) 8.33

(B) 8.5

(C) 8.75

(D) 9

** 59) A ball pen factory decided to reduce its production by 10% over that of previous month for next 3 months starting from February 1994. In January 1994, it produced 3000 ball pens.How many ball pens were produced in March 1994? **

(A) 2700

(B) 2430

(C) 2187

(D) 2400

** 60) A building worth Rs. 133,100 is constructed on land worth Rs.72,900. After how many years will the value of both be the same if land appreciates at 10% p.a and building depreciates at 10% p.a? **

(A) 2.5

(B) 2

(C) 1.5

(D) 3