8 E + 4 F = 48
9 E + 5 F = 55
Fill in the blanks.
- 1 E = _____
- 1 F = _____
- 3 E + 2 F = _____
(a)
8 E + 4 F = 48 --- (1)
9 E + 5 F = 55 --- (2)
Make F the same.
LCM of 4 and 5 = 20
(1) x 5
40 E + 20 F = 240 --- (3)
(2) x 4
36 E + 20 F = 220 --- (4)
(a)
(3) - (4)
(40 E + 20 F) - (36 E + 20 F) = 240 - 220
40 E - 36 E + 20 F - 20 F = 20
4 E = 20
1 E = 20 ÷ 4 = 5
(b)
Substitute E = 5 into (1).
8 E + 4 F = 48
8 x 5 + 4 F = 48
40 + 4 F = 48
4 F = 48 - 40 = 8
1 F = 8 ÷ 4 = 2
(c)
3 E + 2 F
= 3 x 5 + 2 x 2
= 15 + 4
= 19
Answer(s): (a) 5; (b) 2; (c) 19
