7 E + 5 F = 56
8 E + 6 F = 66
Fill in the blanks.
- 1 E = _____
- 1 F = _____
- 4 E + 4 F = _____
(a)
7 E + 5 F = 56 --- (1)
8 E + 6 F = 66 --- (2)
Make F the same.
LCM of 5 and 6 = 30
(1) x 6
42 E + 30 F = 336 --- (3)
(2) x 5
40 E + 30 F = 330 --- (4)
(a)
(3) - (4)
(42 E + 30 F) - (40 E + 30 F) = 336 - 330
42 E - 40 E + 30 F - 30 F = 6
2 E = 6
1 E = 6 ÷ 2 = 3
(b)
Substitute E = 3 into (1).
7 E + 5 F = 56
7 x 3 + 5 F = 56
21 + 5 F = 56
5 F = 56 - 21 = 35
1 F = 35 ÷ 5 = 7
(c)
4 E + 4 F
= 4 x 3 + 4 x 7
= 12 + 28
= 40
Answer(s): (a) 3; (b) 7; (c) 40