Sean has some red and silver marbles. The total mass of all his marbles is 194 g. He has 2 less red marbles than silver marbles. The average mass of the red marbles is 5 g. The average mass of the silver marbles is 7 g. How many marbles does Sean have altogether?
| |
Red |
Silver |
Total |
| Number |
1 u |
1 u + 2 |
2 u + 2 |
| Value |
5 |
7 |
|
| Total value |
5 u |
7 u + 14 |
194 |
Total mass of red marbles
= 1 u x 5
= 5 u
Total mass of silver marbles
= 7(1 u + 2)
= 7 u + 14
Total mass of the marbles
= 5 u + 7 u + 14
= 12 u + 14
12 u + 14 = 194
12 u = 194 - 14
12 u = 180
1 u = 180 ÷ 12 = 15
Total number of marbles
= 2 u + 2
= 2 x 15 + 2
= 30 + 2
= 14
Answer(s): 14
