7000+ Probability Questions for IBPS, SBI PO, SO, Clerk Bank Exams - 1

Ans: D

n(s) = Total possible outcomes = ¹²C₃ = 220

n(E) = Favourable number of cases

= Number of ways of picking 3 marbles (none is blue) out of 7

= ⁷C₃ = $${7 × 6 × 5} / {1 × 2 × 3}$$ = 35

Required probability = $$1 – {35}/{220}$$ = $$1 – {7}/{44}$$ = $${37}/{44}$$.

Ans: B

Here S = {1, 2, 3, 4, 5, 6}.

Let E be the event of getting a multiple of 3.

Then, E = {3, 6}

∴ P(E) = $${n(E)} / {n(S)}$$ = $${2}/{6}$$ = $${1}/{3}$$.

Ans: B

Let S be the sample space.

Then, n(S) = ⁵²C₂ = $$({52 × 51}) / ({2 × 1})$$ = 1326.

Let E = event of getting 2 kings out of 4.

∴ n(E) = ⁴C₂ = $$(4 × 3)/(2 × 1)$$ = 6.

∴ P(E) = $${n(E)} / {n(S)}$$ = $${6}/{1326}$$ = $${1}/{221}$$.

Ans: C

There are 6 favourable cases HHT, HTH, HTT, THT, TTH, THH.

Required probability = $${6}/{8}$$ = $${3}/{4}$$

Ans: B

Sample space S = {HH, HT, TH, TT}

Number of exhaustive cases = 4

There is only one favourable case TT.

∴ P ( 2 tails) = $${1}/{4}$$