ExamHabit
Practise free

JEE Main 2019 · 8 Apr · Shift II

JEE Main 2019 Mathematics question on Probability

The minimum number of times one has to toss a fair coin so that the probability of observing atleast one head is atleast 90% is
  1. A.
    2
  2. B.
    3
  3. C.
    5
  4. D.
    4
Show answer and solution

Correct option: D

Solution

We need 1 - (1/2)n ≥ 0.9, which gives (1/2)n ≤ 0.1.

Taking n=4: (1/2)4 = 1/16 = 0.0625 ≤ 0.1 ✓
Taking n=3: (1/2)3 = 1/8 = 0.125 > 0.1 ✗

So the minimum n is 4.

[JEE Main 2019 · 8 Apr · Shift II]

Practise Probability the way it is asked

A timed set of real JEE Main Probability questions, graded as the exam grades. No sign-up.

Start a Probability test

More: all JEE Main Probability questions · JEE Main 2019 · Mathematics chapter list