Logarithm problems
- 1. The mantissa of log 3274 is 0.5150, then the value of log 32.74 is?
Options- A. 1.5150
- B. 2.5150
- C. 0.5150
- D. 1.5150 Discuss
Correct Answer: 1.5150
Explanation:
Since, 0.3274 gives characteristic 1. Therefore value of log (0.3274) = 1.5150
- 2. If log 5 (x 2 + x) - log 5 x = 2 then the value of x is?
Options- A. 24
- B. 25
- C. 23
- D. 120 Discuss
Correct Answer: 24
Explanation:
? log5[(x2 + x ) / x] = 2
? log10(x + 1) = 2
? x + 1 = 25
? x = 24
- 3. If log a, log b, log c are in A.P. then?
Options- A. a, b, c are in G.P.
- B. a2, b2, c2 are in G.P.
- C. a, b, c are in A.P.
- D. None of these Discuss
Correct Answer: a, b, c are in G.P.
Explanation:
? loga, logb, logc are in A.P. Then,
? logb - loga = logc - logb
? log b/a = log c/b
? b/a = c/b
? b2 = ac
? a, b, c are in G.P.
- 4. The compound interest on Rs. 12,000 for 10 years at the rate of 12% per annum compounded annually is?
Options- A. 25350
- B. 23550
- C. 2550
- D. 25550 Discuss
Correct Answer: 25350
Explanation:
? A = 12,000(1 + 12/100)10
= 12000(28/25)10
? log A = log 12000 + 10[log 28 - log 25]
? log A = 4.0792 + 10(1.4472 - 1.3979)
= 4.0792 + 0.493
= 4.5722
? A = antilog 4.5722 = 37342
C.I. = 37342 - 12000 = 25342
=25350
- 5. The number of digits in the numeral for 2 64?
Options- A. 18 digit
- B. 19 digit
- C. 20 digit
- D. 21digit Discuss
Correct Answer: 20 digit
Explanation:
? x = 264
? log x = log 264
? log x = 64 log 2
= 64 x .3010 = 19.264
? No.of digits = 19 + 1 = 20
- 6. Given log 10 2 = 0.30103, log 10 3 = 0.47712. Find the number of digit, in 3 12 x 2 8?
Options- A. 6
- B. 7
- C. 8
- D. 9 Also asked in: GRE
Correct Answer: 9
Explanation:
Let N = 312 x 28
? log N = 12 x log3 + 8 x log 2
? log N = 12 x 0.47712 + 8 x 0.30103
? log N = 8.13368
? No.of digits = 8 + 1 = 9
- 7. The value of 1/(log 2 ?) + 1/(log 6 ?) is?
Options- A. greater then 1
- B. less than 1
- C. between 5 and 6
- D. None of these Discuss
Correct Answer: greater then 1
Explanation:
Given exp. = 1/(log2 ?) + 1/(log6 ?)
= log? 2 + log? 6
= log? (2 x 6)
= log?12
Since 12 > ? so the value of given expression is more than 1.
- 8. The number of digits in the numeral for (875) 16?
Options- A. 47 digit
- B. 48 digit
- C. 49 digit
- D. 50 digit Discuss
Correct Answer: 48 digit
Explanation:
? N = (875)16
? log N = log (875)16
? log N = 16 log (875)
= 16 x (2.942)
= 47.072
? No.of digits = 47 + 1 = 48
- 9. The population of a town at the beginning of the year 1986 was 2,65,000. If the rate of increase be 52 per thousand of the population. Find the population at the beginning of the year 1991.?
Options- A. 3,40,400
- B. 3,41,400
- C. 3,42,400
- D. 3,43,400 Discuss
Correct Answer: 3,41,400
Explanation:
We have r = Rate of increase
= 52/1000 x 100
= 5.2, n = 5, P0 = 265000
? P = 265000(1 + 5.2 / 100)5
? log P = log 265000 + 5(log 105.2 - log 100)
= 5.4232 + 5(2.0220 - 2)
= 5.4232 + 0.1100
= 5.5332
? P = antilog(5.5332) = 341400
- 10. What rate per cent per annum compound interest will Rs. 3,000 in 3 years if the interest is reckoned half yearly?
Options- A. 12%
- B. 13%
- C. 14%
- D. 15% Discuss
Correct Answer: 14%
Explanation:
? 3000 = 2000(1 + r/200)6
? 3/2 = (1 + r/200)6
? 1 + r/200 = (3/2)1/6
? log(1 + r/200)= 1/6(log 3 - log 2 )
? log(1 + r/200)= 1/6(0.4771-.3010)
= 0.02935
? (1 + r/200) = antilog(.02935)
? 1 + r/200 = 1.070 = 1 + 7/100
? r = 14%
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