How do you find four consecutive multiples of 5 whose sum is 90?

3 Answers
May 2, 2018

#15,20,25,30#

Explanation:

We know that the multiples' will add up to 90, so their average must be #90/4#, or #22.5#. Since there are an even number of multiples (4), none of them will touch the average, but they will be centered around it. Therefore, the multiples must be #15,20,25,30#
Check:
#15+20+25+30=90#

May 2, 2018

#15#, #20#, #25# and #30#

Explanation:

Let the smallest number of the bunch be #x#,

#x+(x+5)+(x+5+5)+(x+5+5+5)=90#

Simplify,

#4x+30=90#

Subtract #30# from both sides,

#4x=60#

Divide,

#x=15#

Since the smallest number is #15#, the rest are as follows: #20#, #25# and #30#.

May 2, 2018

The multiples are #" "15," "20," "25," "30#

Explanation:

Any multiple of #5# can be written as #5x#

The next multiple will be when #x# increases by #1#

The sum of four consecutive multiples of #5# is #90#

#5x +5(x+1)+5(x+2)+5(x+3)=90#

#5x +5x+5+5x+10+5x+15 = 90#

#20x +30 =90#

#20x = 60#

#x =3#

So the first multiple of #5# is #5xx3=15#

The multiples are #" "15," "20," "25," "30#