VERITAS Prep Solution:

Solution: The easiest way to solve this question may be to visually present the given information using a number line:

Attachment:

Screen Shot 2018-10-03 at 12.17.58 AM.png [ 38.82 KiB | Viewed 268 times ]
Since we know number of people who are less than 18 yrs old (420), and also those who are 18 yrs and more (690), we know the total population would be the sum of the two groups, i.e., 420 + 690 = 1110.

Using this, we can determine the number of people who are less than 25 yrs is 1110 – 510 = 600. So to find number of people who are between the ages of 18 and 25, we simply subtract the number of people below age 18. 600 – 420 = 180.

The number of people of age 40 yrs or more is 1110 – 810 = 300. We subtract this from the number of people age 25 years or more to find the group older than 25 and younger than 40, i.e., 510 – 300 = 210. The ratio between these two groups is 180:210, or 6:7.

_________________

Please award kudos, If this post helped you in someway.