11 Plus Exams Forum

Hi

I am confused with this sequence question

The answer is 17 but i cannot understand how to get to it ???

39 37 35 33 30 28 24 22 ----

Please would someone put me out of my misery

Thanks

Amanda123 wrote: 39 37 35 33 30 28 24 22 ----

Please would someone put me out of my misery

Thanks

-2 -2 -2 -3 -2 -4 -2 -?

two sequences -2 alternated with

-2 -3 -4 -? so -5

22-5=17

I think its the -2 -2 -2 at the start that confuses.


steve

39 37 35 33 30 28 24 22 ----

This is 2 series sets interleaved with

the odd series terms 39 35 30 24 ... being the 1st set and

the even series terms 37 33 28 22 being the 2nd set

For both series the differences between the terms are -4, -5, -6 etc

the next term in the 1st series is therefore 24 - 7 = 17

A good quick trick is to count the total number of terms in the series - if it's 6 or more it often means there are 2 series interleaved. Single series often only have 5 terms.

[quote="KenR"][quote]39 37 35 33 30 28 24 22 ----
[/quote]

This is 2 series sets interleaved with

the odd series terms 39 35 30 24 ... being the 1st set and

the even series terms 37 33 28 22 being the 2nd set

For both series the differences between the terms are -4, -5, -6 etc

the next term in the 1st series is therefore 24 - 7 = 17

A good quick trick is to count the total number of terms in the series - if it's 6 or more it often means there are 2 series interleaved. Single series often only have 5 terms.[/quote]