This problem is pretty tough. We can certainly solve it using algebra but that seems a bit complex. Instead, first, let's find out what percent of people are both in the relevant age group and fully employed, for both age groups. Those aged 3544 are 21% of the total population, and of this group, 90% are fully employed. If we round to 20% and multiply, we find that 20%x90% = 18%. Similarly, for those aged 5564, representing 11% of the population, which we can round to 10%, and multiplied by the 40% that are fully employed, we find that fully employed 5564 yearolds represent 10%x40% = 4% of the total population. So we have a ratio of 18:4, or 9:2, younger to older people.
We've also been told that the younger group produced 900 volunteers, so since the ratio is 9:2, we would expect the older group to produce 200 volunteers. However, we also know that the younger group volunteered 3 times more than the older group, so if we divide 200 by 3, we find that the older group produced about 67 volunteers.
Thus, if in 2009, 65 new older people began volunteering, we can say that they increased by about 100%, giving us an answer of E.
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