correcting mistakes from november mocks

Question 1

• the ratio of blue to white vans is 4:3
• for blue vans, the ratio of small to large vans is 3:5
• work out the fraction of the number of vans made in the factory that are blue and large

Answer 1

• we can say that 4:3 is equal to 4x:3x
• we can say that 3:5 is equal to 3y:5y
• using this the ratio, 4x = 3y + 5y
• 4x = 8y
• rearrange the formula to make x/y = 2
• the total of ratio 4x:3x = 7x
• since we need to find the fraction of large vans, the fraction of large blue vans to the total is 7x/5y
• substitute x/y for 2
• 7/5 * 2 = 14/5

Question 2

• in a class, there are 11 boys and 19 girls
• the mean weight of all 30 children is 32.85kg
• the mean weight of the 11 boys is 31.9kg
• work out the mean weight of the girls

Answer 2

• total/amount = mean
• total/30 = 32.85kg
• 30 x 32.85 = 985.5
• 11 x 31.9 = 350.9
• 985.5/350.9 = 634.6 = total for girls
• 634.6 / 19 = 33.4