Mark has 90% as many pens as Luis. If Mark gives away 50% of the pens and Luis gives away 75% of his pens, they will have 84 pens altogether. How many pens do the two of them have?
| |
Mark |
Luis |
Total |
Comparing Mark
and Luis at first |
9x2 =
18 u |
10x2 =
20 u |
|
| Before |
2x9 =
18 u |
4x5 =
20 u |
|
| Change |
- 1x9 =
- 9 u |
- 3x5 =
- 15 u |
|
| After |
1x9 =
9 u |
1x5 =
5 u |
84 |
90% =
90100 =
910 50% =
50100 =
12 75% =
75100 =
34 The number of pens that Mark has at first is repeated. Make the number of pens that Mark has the same. LCM of 9 and 2 is 18 u.
The number of pens that Luis has at first is repeated. Make the number of pens that Luis has the same. LCM of 10 and 4 is 20 u.
Number of pens in the end
= 9 u + 5 u
= 14 u
14 u = 84
1 u = 84 ÷ 14 = 6
Total number of pens that the two of them have
= 18 u + 20 u
= 38 u
= 38 x 6
= 228
Answer(s): 228
