At a certain restaurant, there are 25 tables, and each table has either 2 or 4 chairs. If a total of 86 chairs accompany the 25 tables, how many tables have exactly 4 chairs? Show your work
25*2=50
86-50=36
36/2=18
25-18=7
17*2+18*4
Tables use at least 2 chairs. 25 tables require 50 of the 86 chairs. The remaining 36 chairs are supplied 2 per table by 18 tables.
t + f = 25
2t + 4f = 86
2t + 2f = 50
---------------------
2f = 36
f = 18
18 tables have exactly 4 chairs
x = tables with 4 chairs
y = tables with 2 chairs
Number of tables: x + y = 25 → y = 25-x
Number of chairs: 4x+2y = 86 → 4x + 2(25-x) = 86
4x - 2x = 86-50
2x = 36
x = 18
18 tables have 4 chairs
Comments
25*2=50
86-50=36
36/2=18
25-18=7
17*2+18*4
Tables use at least 2 chairs. 25 tables require 50 of the 86 chairs. The remaining 36 chairs are supplied 2 per table by 18 tables.
t + f = 25
2t + 4f = 86
2t + 2f = 50
---------------------
2f = 36
f = 18
18 tables have exactly 4 chairs
x = tables with 4 chairs
y = tables with 2 chairs
Number of tables: x + y = 25 → y = 25-x
Number of chairs: 4x+2y = 86 → 4x + 2(25-x) = 86
4x - 2x = 86-50
2x = 36
x = 18
18 tables have 4 chairs