There are some balls of red, green and yellow colour lying on a table. There are as many red balls as there are yellow balls. There are twice as many yellow balls as there are green ones. The number of red balls.

Correct Option (B)

Let R represent the number of red balls, Y the number of yellow balls, and G the number of green balls.

According to the problem statement:

• "There are as many red balls as there are yellow balls." This translates to the equation: R = Y.
• "There are twice as many yellow balls as there are green ones." This translates to the equation: Y = 2G.

By substituting the second equation (Y = 2G) into the first equation (R = Y), we derive the relationship: R = 2G.

Therefore, the number of red balls is double the number of green balls.

Incorrect Options:

The fundamental relationships established are R = Y and Y = 2G, which implies R = 2G.

Option (A): is equal to the sum of yellow and green balls.

The sum of yellow and green balls is Y + G. Since Y = 2G, this sum becomes 2G + G = 3G. As R = 2G, R is not equal to 3G. Hence, this option is incorrect.

Option (C): is equal to yellow balls minus green balls.

Yellow balls minus green balls is Y - G. Since Y = 2G, this difference becomes 2G - G = G. As R = 2G, R is not equal to G. Hence, this option is incorrect.

Option (D): cannot be ascertained.

The given conditions provide sufficient information to establish a direct and definite relationship between the number of red balls and green balls (R = 2G). Therefore, the number of red balls can be ascertained in relation to the number of green balls. Hence, this option is incorrect.