It's quite simple once you learn the technique. The basic idea is to break it down into intervals. What is the smallest interval between two numbers that will match the criteria? The first number would be 324,713. The second number would be 324,813. So the smallest interval is 100.
1) Find the lowest and highest numbers that match the criteria in the range: 324,713 and 458,513
2) Subtract lowest from highest then divide by the interval:
(458,513 - 324,713)/100 = 1338
3) Add 1 to the result: 1339
The basic formula is one that you will need again and again:
The number of integers given a particular range: B - A + 1 where B is the high integer and A is the low integer
The formula used above is a variation of this formula:
(B - A) / (interval size) + 1
Memorize both. You will see it again. And again. And again.
* I have seen other people that just divide the number by the interval straight out without determining the low and high value, but I feel this could lead to a situation where you're not quite sure of the accuracy (e.g. answer choices contain both 1339 and 1338 and a rounding error can influence the result). Finding the low and high value takes only a few extra seconds, but is guaranteed to be accurate.
1) Find the lowest and highest numbers that match the criteria in the range: 324,713 and 458,513
2) Subtract lowest from highest then divide by the interval:
(458,513 - 324,713)/100 = 1338
3) Add 1 to the result: 1339
The basic formula is one that you will need again and again:
The number of integers given a particular range: B - A + 1 where B is the high integer and A is the low integer
The formula used above is a variation of this formula:
(B - A) / (interval size) + 1
Memorize both. You will see it again. And again. And again.
* I have seen other people that just divide the number by the interval straight out without determining the low and high value, but I feel this could lead to a situation where you're not quite sure of the accuracy (e.g. answer choices contain both 1339 and 1338 and a rounding error can influence the result). Finding the low and high value takes only a few extra seconds, but is guaranteed to be accurate.
