CAT 2021 Quant was dominated by Arithmetic followed by Algebra. In Arithmetic, the questions were dominated by topics like Speed-time-distance, Mixture and Alligations. This year, there was a surprise. The questions from Geometry were relatively on the lower side as compared to the previous years. There were 8 TITA Qs this year. Overall this section was at a medium level of difficulty.
Question 7 : A box has 450 balls, each either white or black, there being as many metallic white balls as metallic black balls. If 40% of the white balls and 50% of the black balls are metallic, then the number of non-metallic balls in the box is
The box contains 450 balls
Let’s consider the number of white and black balls to be ‘x’ and ‘y’ respectively.
The number of white metallic balls is the same as black metallic balls.
40% of the white balls and 50% of the black balls are metallic.
So, 0.4x =0.5y
x : y = 5 : 4.
Hence the number of White balls is 250 (100 - metallic and 150 - Non-metallic)
Hence the number of Black balls is 200 (100 - metallic and 100 - Non-metallic)
The total number of non-metallic balls is 250.
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