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Q:

Which of the following statements is not correct?

A) log10 = 1	B) log (2 + 3) = log (2 x 3)
C) log1 = 0	D) log (1 + 2 + 3) = log 1 + log 2 + log 3

Answer & Explanation Answer: B) log (2 + 3) = log (2 x 3)

Explanation:

log (2 + 3) = log 5

log (2 x 3) = log 2 + log 3

log (2 + 3) $\neq$ log (2 x 3)

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Filed Under: Logarithms
Exam Prep: Bank Exams
Job Role: Bank PO

Q:

A brother and a sister appear for an interview against two vacant posts in an office. The probability of the brother’s selection is 1/5 and that of the sister’s selection is 1/3. What is the probability that only one of them is selected?

A) 1/5	B) 3/4
C) 2/5	D) 3/5

Answer & Explanation Answer: C) 2/5

Explanation:

Probability that only one of them is selected = (prob. that brother is selected) × (prob. that sister is not selected) + (Prob. that brother is not selected) × (Prob. that sister is selected)

= $(\frac{1}{5} * \frac{2}{3}) + (\frac{4}{5} * \frac{1}{3})$ = $\frac{2}{5}$

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Filed Under: Probability

Q:

A rectangular block 6 cm by 12 cm by 15 cm is cut up into an exact number of equal cubes. Find the least possible number of cubes.

A) 30	B) 40
C) 10	D) 20

Answer & Explanation Answer: B) 40

Explanation:

Volume of the block = (6 x 12 x 15) cu.cm = 1080 cu.cm

Side of the largest cube = H.C.F. of 6 cm, 12 cm, 15 cm

= 3 cm.

Volume of this cube = (3 x 3 x 3) cu.cm = 27 cu.cm

Number of cubes = $\frac{1080}{27}$ = 40.

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Filed Under: Volume and Surface Area

Q:

Find the number of bricks, each measuring 24 cm x 12 cm x 8 cm, required to construct a wall 24 m long, 8m high and 60 cm thick, if 10% of the wall is filled with mortar?

A) 35000	B) 45000
C) 55000	D) 65000

Answer & Explanation Answer: B) 45000

Explanation:

Volume of the wall = (2400 x 800 x 60) cu.cm

Volume of bricks = 90% of the volume of the wall

= [(90/100) x 2400 x 800 x 60] cu.cm

Volume of 1 brick = (24 x 12 x 8) cu.cm

Number of bricks = [(90/100) x (2400 x 800 x 60) ]/ (24 x 12 x 8) = 45000

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Filed Under: Volume and Surface Area

Q:

Find the length of the longest pole that can be placed in a room 12 m long 8m broad and 9m high.

A) 14m	B) 15m
C) 16m	D) 17m

Answer & Explanation Answer: D) 17m

Explanation:

Length of longest pole = Length of the diagonal of the room

$[\sqrt{12^{2} + 8^{2} + 9^{2}}] = \sqrt{289} = 17 m$

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Filed Under: Volume and Surface Area

Q:

I forgot the last digit of a 7-digit telephone number. If 1 randomly dial the final 3 digits after correctly dialing the first four, then what is the chance of dialing the correct number?

A) 1/999	B) 1/1001
C) 1/1000	D) 4/1000

Answer & Explanation Answer: C) 1/1000

Explanation:

It is given that last three digits are randomly dialled. then each of the digit can be selected out of 10 digits in 10 ways.
Hence required probability = ${(\frac{1}{10})}^{3}$ = 1/1000

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Filed Under: Probability

Q:

What is the probability of getting at least one six in a single throw of three unbiased dice?

A) 1/36	B) 91/256
C) 13/256	D) 43/256

Answer & Explanation Answer: B) 91/256

Explanation:

Find the number of cases in which none of the digits show a '6'.

i.e. all three dice show a number other than '6', 5×5×5=125 cases.

Total possible outcomes when three dice are thrown = 216.

The number of outcomes in which at least one die shows a '6' = Total possible outcomes when three dice are thrown - Number of outcomes in which none of them show '6'.

=216−125=91

The required probability = 91/256

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Filed Under: Probability

Q:

The probability of success of three students X, Y and Z in the one examination are 1/5, 1/4 and 1/3 respectively. Find the probability of success of at least two.

A) 1/4	B) 1/2
C) 1/6	D) 1/3

Answer & Explanation Answer: C) 1/6

Explanation:

P(X) = $\frac{1}{5}$ , P(Y) = $\frac{1}{4}$ , P(Z) = $\frac{1}{3}$

Required probability:

= [ P(A)P(B){1−P(C)} ] + [ {1−P(A)}P(B)P(C) ] + [ P(A)P(C){1−P(B)} ] + P(A)P(B)P(C)

= $(\frac{1}{4} * \frac{1}{3} * \frac{4}{5}) + (\frac{3}{4} * \frac{1}{3} * \frac{1}{5}) + (\frac{2}{3} * \frac{1}{4} * \frac{1}{5}) + (\frac{1}{4} * \frac{1}{3} * \frac{1}{5})$

= $\frac{4}{60} + \frac{3}{60} + \frac{2}{60} + \frac{1}{60}$ = $\frac{10}{60}$ = $\frac{1}{6}$

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Filed Under: Probability

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