Jack

10-10-2013, 11:05 AM

How can we find the multiples of 4 between 278 and 679, inclusive?

View Full Version : SAT math multiples question

Jack

10-10-2013, 11:05 AM

How can we find the multiples of 4 between 278 and 679, inclusive?

miranda

10-10-2013, 11:06 AM

This can be solved using arithmetic sequences. We know that the nth term of an arithmetic sequence is given by the following formula:

a_{n}= a_{1} +(n-1)d, where a_{1} is the first term of the sequence (in our case is 280 since is the first multiple of 4 starting from 278) and d is the common difference of the progression (in our case the difference equals 4). The last term of the sequence is the number 676 which is the greater multiple of 4 less or equal than 679.

Therefore

676=280 +(n-1)4

4n=676-280+4

4n=400

n=100

a_{n}= a_{1} +(n-1)d, where a_{1} is the first term of the sequence (in our case is 280 since is the first multiple of 4 starting from 278) and d is the common difference of the progression (in our case the difference equals 4). The last term of the sequence is the number 676 which is the greater multiple of 4 less or equal than 679.

Therefore

676=280 +(n-1)4

4n=676-280+4

4n=400

n=100

Jack

10-10-2013, 11:06 AM

Thanks miranda!

Powered by vBulletin® Version 4.2.2 Copyright © 2018 vBulletin Solutions, Inc. All rights reserved.