Question

Two cubes have their faces painted either red or blue . The first cube has 5 red faces and 1 blue face .When the two cubes are rolled simultaneously , the probability that the two top faces show the same colour is ½.number of red faces on the second cube, Is ?

Answer 1

no. of red faces=n 
no. of blue faces=6-n
P(getting same colour)=$\frac{5}{6} ×  \frac{n}{6} +\frac{1}{6} ×   \frac{6-n}{6} =\frac{1}{2}$
4n+6=18
4n=12
n=3
∴,number of red faces is 3

Answer 2

Answer:

The number of red faces on second cube is 3 faces.

Step-by-step explanation:

Given that two cubes have their faces painted either red or blue. The first cube has 5 red faces and 1 blue face. When the two cubes are rolled simultaneously, the probability that the two top faces show same color is ½.

we have to find the number of red faces on the second cube.

Let the second cube has n red faces ∴ (6-n) blue faces

First cube: Red faces=5

Blue faces=1

$\text{The probability that the two top faces show the same color is } \frac{1}{2}$

$\frac{5}{6}\times \frac{n}{6}+\frac{1}{6}\times \frac{6-n}{6}=\frac{1}{2}$

$\frac{5n}{36}+\frac{6-n}{36}=\frac{1}{2}$

$\frac{4n+6}{36}=\frac{1}{2}$

$4n=18-6=12$

$n=3$

The number of red faces on second cube is 3 faces.