Multiple choice

The mean weight of 100 students in a class is 46 kg. The mean weight of boys is 50 kg and that of girls is 40 kg. The number of boys exceeds the number of girls by:

  1. 10

  2. 15

  3. 20

  4. 25
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let B be number of boys, G be number of girls. B + G = 100. (50B + 40G) / 100 = 46. 50B + 40G = 4600. 50B + 40(100 - B) = 4600. 50B + 4000 - 40B = 4600. 10B = 600, B = 60. Then G = 40. Difference = 60 - 40 = 20.

AI explanation

Let the number of boys be B and the number of girls be G. Using the combined mean formula, 46 multiplied by 100 equals 50B plus 40G, which simplifies to 5B + 4G = 460. We also know B + G = 100, so substituting G = 100 - B gives 5B + 400 - 4B = 460, resulting in B = 60 and G = 40. The number of boys exceeds the number of girls by 20.

Keep practicing — related questions