UPSC Prelims 2013·CSAT·Quantitative Aptitude·Arithmetic

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

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  1. Ais equal to the sum of yellow and green balls
  2. Bis double the number of green ballsCorrect
  3. Cis equal to yellow balls minus green balls
  4. Dcannot be ascertained.

Explanation

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

From the first statement: "There are as many red balls as there are yellow balls." This means R = Y.

From the second statement: "There are twice as many yellow balls as there are green ones." This means Y = 2 * G.

Now, we want to find the relationship for the number of red balls (R). Since R = Y and Y = 2G, we can substitute Y in the first equation: R = 2G.

Let's analyze the options: A) is equal to the sum of yellow and green balls (R = Y + G). We know R = Y, so Y = Y + G, which implies G = 0. This is not generally true. B) is double the number of green balls (R = 2G). This matches our derived relationship. So, B is correct. C) is equal to yellow balls minus green balls (R = Y - G). We know R = Y, so Y = Y - G, which implies G = 0. This is not generally true. D) cannot be ascertained. We were able to ascertain the relationship, so this is incorrect.

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

The final answer is B

Quantitative Aptitude: There are some balls of red, green and yellow colour lying on a table. There are as many red balls as there are yellow b
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