7 N + 4 P = 79
8 N + 5 P = 92
Fill in the blanks.
- 1 N = _____
- 1 P = _____
- 5 N + 3 P = _____
(a)
7 N + 4 P = 79 --- (1)
8 N + 5 P = 92 --- (2)
Make P the same.
LCM of 4 and 5 = 20
(1) x 5
35 N + 20 P = 395 --- (3)
(2) x 4
32 N + 20 P = 368 --- (4)
(a)
(3) - (4)
(35 N + 20 P) - (32 N + 20 P) = 395 - 368
35 N - 32 N + 20 P - 20 P = 27
3 N = 27
1 N = 27 ÷ 3 = 9
(b)
Substitute N = 9 into (1).
7 N + 4 P = 79
7 x 9 + 4 P = 79
63 + 4 P = 79
4 P = 79 - 63 = 16
1 P = 16 ÷ 4 = 4
(c)
5 N + 3 P
= 5 x 9 + 3 x 4
= 45 + 12
= 57
Answer(s): (a) 9; (b) 4; (c) 57
