10 girls and 15 boys sit a test. The mean mark for the boys is 70. The mean mark for girls is 82. Work out the mean mark for the whole class.
boys' total = 70 x 15 = 1050 girls' total = 82 x 10 = 820 Total = 1870 mean = 1870/ 25 = 74.3
boys' total = 70 x 15 = 1050 girls' total = 82 x 10 = 820 Total = 1870 mean = 1870/ 25 = 74.3
