Fractions of Quantities Mathematics Fractions of Quantities

Lesson Objectives The aim of this powerpoint is to help you… to calculate fractions of quantities to revise multiplying fractions by fractions

Method 1 Write the quantity over 1 and treat as you would when multiplying two fractions together… Multiply the top numbers together Multiply the bottom numbers together Cancel down (if possible) and/or convert your improper fraction back into a mixed number

40 40 Example – Using method 1 120 ÷ 3 Find 2/3 of 60 Remember the line in a fraction means divide, so… 120 3 2 60 3 1 2×60 120 3×1 3 40 × = = = 40 120 ÷ 3  =

Method 2 Remember that ‘of’ in maths means multiply so… Multiply the quantity by the top number of the fraction Remember the line in a fraction tells you to divide so… Divide your product by the bottom number of the fraction

40 Example – Using method 2 60 (2 x 60) ÷ 3 = 2 3 ×  Find 2/3 of 60 (120) 2 3 60 40 × (2 x 60)  ÷ 3 =

Method 3 Find the unitary fraction of the quantity by dividing the quantity by the bottom of the fraction… Then multiply this by the top number of the fraction.

20 40 Example – Using method 3 60 60 60 ÷ 3 = 2 × 20 = 1 3 of  2 3 of Find 2/3 of 60 1 3 of 60 20 60 ÷ 3 =  2 3 of 60 40 2 × 20 = 

Quick Practice of 40 of 49kg of 40 of 81p of 300cm of £3 A 1 D 2 5 7 5 7 B 3 E 4 5 9 C 5 F 7 6 10 Work out your answers before clicking on to the next slide. of 40 of 49kg of 40 of 81p of 300cm of £3 HINT: Convert to pence first!

Answers A 1 5 of 40 = B 3 5 of 40 = C 5 6 of 300 = D 2 7 of 49 = E 4 9 of 81 = F 7 10 of 300p = 40 ÷ 5 = 8 (49 ÷ 7) then x 2 = 14kg (40 ÷ 5) then x 3 = (81 ÷ 9) then x 4 = 24 36p (300 ÷ 6) then x 5 = (300 ÷ 10) then x 7 = 250cm 210p or £2.10

What next? Print out the notes called Frac8. Read them and make sure you answer any questions Work through pages 1, 2, 3 & 8 of the MyMaths lesson called More Fractions found at: http://www.mymaths.co.uk/tasks/library/loadLesson.asp?title=fractions/fractionsGold&taskID=1370 Work through pages 7 to 10 of the MyMaths lesson called Fractions of Amounts found at: http://www.mymaths.co.uk/tasks/library/loadLesson.asp?title=fractions/fractions1&taskID=1018 If you need more practice, try the worksheet called FracAm-S2.xlsx. Now move on to the Frac-9 powerpoint