A bag contains 6 white and 4 black balls .2 balls are drawn at random. Find the

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Question
A bag contains 6 white and 4 black balls .2 balls are drawn at random. Find the probability that they are of same colour.
Options
A. 1/2
B. 7/15
C. 8/15
D. 1/9

Correct Answer

7/15

Explanation

Let S be the sample space

Then n(S) = no of ways of drawing 2 balls out of (6+4) = $10 C_{2}$ 10 = $\frac{10 * 9}{2 * 1}$ =45

Let E = event of getting both balls of same colour

Then,n(E) = no of ways (2 balls out of six) or (2 balls out of 4)

= $6 C_{2} + 4 C_{2}$ = $\frac{6 * 5}{2 * 1} + \frac{4 * 3}{2 * 1}$ = 15+6 = 21

Therefore, P(E) = n(E)/n(S) = 21/45 = 7/15

2.
Two posts are x meter apart and the height of one is double that of the other. If from the midpoint of the line joining their feet, an observer finds the angular elevations of their tops to be complementary, then the height (in meter) of the shorter post is :
Options
A. x 2 ?2
B. x 4
C. x ?2
D. x ?2

10.
A sum of ? 4000 is lent out in two parts, one at 8% simple interest and other at 10% simple interest. If the annual interest is ? 352, the sum lent at 8% is
Options
A. ? 1600
B. ? 2400
C. ? 1800
D. ? 2800

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