Arithmetic
Number System-Natural numbers, Integers, Rational and Real numbers, Fundamental operations, addition, subtraction, multiplication, division, Square roots, Decimal fractions. Unitary method-time and distance, time and work, percentages, applications to simple and compound interest, profit and loss, ratio and proportion, variation. Elementary Number Theory – Division algorithm. Prime and composite numbers. Tests of divisibility by 2, 3, 4, 5, 9 and 11. Multiples and factors. Factorization Theorem. H.C.F. and L.C.M. Euclidean algorithm. Logarithms to base 10, laws of logarithms, use of logarithmic tables.
Sample Questions
1. If 6 men and 8 boys can do a piece of work in 10 days while 26 men and 48 boys can do the same in 2 days, the time taken by 15 men and 20 boys in doing the same type of work will be:
- 4 days
- 5 days
- 6 days
- 7 days
Answer: 1
Solution:Let 1 man's 1 day's work = x and 1 boy's 1 day's work = y.
Then, 6x + 8y = 1/10 and 26x + 48y = 1/2.
Solving these two equations, we get : x =1/100 and y = 1/200.
(15 men + 20 boy)'s 1 day's work = 15/100 + 20/200 = 1/4.
=>15 men and 20 boys can do the work in 4 days.
2. If a person walks at 14 km/hr instead of 10 km/hr, he would have walked 20 km more. The actual distance travelled by him is:
- 50 km
- 56 km
- 70 km
- 80 km
Answer: 1
Solution:Let the actual distance travelled be x km.
Then, x/10 = (x + 20)/14
14x = 10x + 200
=> 4x = 200
=> x = 50 km.
3. A sum of money is to be distributed among A, B, C, D in the proportion of 5 : 2 : 4 : 3. If C gets Rs. 1000 more than D, what is B's share?
- Rs. 500
- Rs. 1500
- Rs. 2000
- None of these
Answer: 3
Solution:Let the shares of A, B, C and D be Rs. 5x, Rs. 2x, Rs. 4x and Rs. 3x respectively.
Then, 4x - 3x = 1000
=> x = 1000.
B's share = Rs. 2x = Rs. (2 x 1000) = Rs. 2000.
4. A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is:
- Rs. 650
- Rs. 690
- Rs. 698
- Rs. 700
Answer: 3
Solution:S.I. for 1 year = Rs. (854 - 815) = Rs. 39.
S.I. for 3 years = Rs.(39 x 3) = Rs. 117.
=> Principal = Rs. (815 - 117) = Rs. 698.
5. In a certain store, the profit is 320% of the cost. If the cost increases by 25% but the selling price remains constant, approximately what percentage of the selling price is the profit?
- 30%
- 70%
- 100%
- 250%
Answer: 2
Solution:Let C.P.= Rs. 100. Then, Profit = Rs. 320, S.P. = Rs. 420.
New C.P. = 125% of Rs. 100 = Rs. 125
New S.P. = Rs. 420.
Profit = Rs. (420 - 125) = Rs. 295.
Required percentage = [(295/450)*100]% = [1475/21]%= 70% (approx)
6. Which of the following statements is not correct?
- log10 10 = 1
- log (2 + 3) = log (2 x 3)
- log10 1 = 0
- log (1 + 2 + 3) = log 1 + log 2 + log 3
Answer: 2
Solution:(a) Since log
a a = 1, so log
10 10 = 1.
(b) log (2 + 3) = log
5 and log (2 x 3) = log 6 = log 2 + log 3
=> log (2 + 3) log (2 x 3)
(c) Since loga 1 = 0, so log10 1 = 0.
(d) log (1 + 2 + 3) = log 6 = log (1 x 2 x 3) = log 1 + log 2 + log 3.
So, (b) is incorrect.
7. If log 27 = 1.431, then the value of log 9 is:
- 0.934
- 0.945
- 0.954
- 0.958
Answer: 3
Solution:log 27 = 1.431
log (
33 ) = 1.431
3 log 3 = 1.431
log 3 = 0.477
=> log 9 = log(32 ) = 2 log 3 = (2 x 0.477) = 0.954.
8. A vendor bought toffees at 6 for a rupee. How many for a rupee must he sell to gain 20%?
- 3
- 4
- 5
- 6
Answer: 3
Solution:C.P. of 6 toffees = Re. 1
S.P. of 6 toffees = 120% of Re. 1 = Rs. 6/5
For Rs. 6/5, toffees sold = 6.
5
For Re. 1, toffees sold = [6 x(5/6) = 5.
9. A takes twice as much time as B or thrice as much time as C to finish a piece of work. Working together, they can finish the work in 2 days. B can do the work alone in:
- 4 days
- 6 days
- 8 days
- 12 days
Answer: 2
Solution:Suppose A, B and C take x, x/2, and x/3 days respectively to finish the work.
Then,[(1/x)+(2/x)+(3/x)] = 1/2
=> 6/c = 1/2
=> x = 1
So, B takes (12/2) = 6 days to finish the work.
10. Factors of the equation 4x2 + 20 x +25 is _______.
- (2x +5)(2x +5)
- (2x -5)(2x -5)
- (3x +5)(5x +5)
- (2x +3)(2x -5)
Answer: 1
Solution:a
2 +2ab +b
2 = ( a+b)
2
(2x )
2 + 2 (2x)(5) +(5)
2
=(2x + 5)
2
Factors are (2x +5)(2x +5)