Tip: in the print dialog, untick Headers and footersunder More settings — the date and URL in the margin are your browser's, not part of the sheet.
DANEMATHICS
www.danemathics.com
/ 18
MEMORANDUM
Name:
Class:
Date:
Video: Adding & Subtracting Common Fractions · Grade 8–9
These are the questions worked through in the video. Pause after each one, do it yourself, then check against the video.
These are the questions worked through in the video. Pause after each one, do it yourself, then check against the video.
- Find the LCM of the two denominators.
- Draw one long division line and write the LCM underneath.
- Ask: how many times does each denominator go into the LCM? Multiply that answer by its numerator, above the line.
- Bring the + or − down and work out the top.
SECTION A — ADDING
1.
Calculate:3/8 + 1/4
LCM of 8 and 4 is 8
8 goes into 8 1 time → 1 × 3 = 3 | 4 goes into 8 2 times → 2 × 1 = 2
= (3 + 2)/8 = 5/8
(2)
2.
Calculate:5/6 + 2/9
LCM of 6 and 9 is 18
6 goes into 18 3 times → 3 × 5 = 15 | 9 goes into 18 2 times → 2 × 2 = 4
= (15 + 4)/18 = 19/18
(2)
3.
Calculate:2/5 + 3/10
LCM of 5 and 10 is 10
5 goes into 10 2 times → 2 × 2 = 4 | 10 goes into 10 1 time → 1 × 3 = 3
= (4 + 3)/10 = 7/10
(2)
4.
Calculate:4/7 + 13/14TRY IT YOURSELF
LCM of 7 and 14 is 14
7 goes into 14 2 times → 2 × 4 = 8 | 14 goes into 14 1 time → 1 × 13 = 13
= (8 + 13)/14 = 21/14
(3)
SECTION B — SUBTRACTING
5.
Calculate:2/3 − 6/4
LCM of 3 and 4 is 12
3 goes into 12 4 times → 4 × 2 = 8 | 4 goes into 12 3 times → 3 × 6 = 18
= (8 − 18)/12 = −10/12
(2)
6.
Calculate:3/2 − 6/4
LCM of 2 and 4 is 4
2 goes into 4 2 times → 2 × 3 = 6 | 4 goes into 4 1 time → 1 × 6 = 6
= (6 − 6)/4 = 0/4 = 0
(2)
7.
Calculate:9/18 − 2/9
LCM of 18 and 9 is 18
18 goes into 18 1 time → 1 × 9 = 9 | 9 goes into 18 2 times → 2 × 2 = 4
= (9 − 4)/18 = 5/18
(2)
8.
Calculate:2/4 − 3/6TRY IT YOURSELF
LCM of 4 and 6 is 12
4 goes into 12 3 times → 3 × 2 = 6 | 6 goes into 12 2 times → 2 × 3 = 6
= (6 − 6)/12 = 0/12 = 0
(3)
TOTAL: 18