A theme park has a log that can hold 12 people. They also have a weight limit of 1500 lbs per log for safety reason. If the average adult weighs 150 lbs, the average child weighs 100 lbs and the log itself weights 200, the ride can operate safely if the inequality
150A+100C+200<1500

<=less or equal

Is satisfied (A is the number of adults and C is the number of children in the log ride together). THere are several groups of children of differing numbers waiting to ride. Groups one has 4 children, group two has 3 children, group three has 9 children, group four 6 children while group five has 5 children.
If 4 adults are already seated in the log, which groups of children can safely ride with them? Explain please~



Answer :

If 4 adults are already in the log, then 150*4 = 600
600 + 100C + 200 = 1500
Re-arranged, 100C = 1500 - 600 - 200
Or simply
100C = 700
Divide each side by 100 to isolate C
So C = 7
So a maximum of 7 children can be seated in the log
All the groups except group 3 can be in the log