#### Challenge "Number Sequence — Part 2" ¶

By: admin on July 11, 2011, 2:35 p.m.

This sequence is infinite, the first 9 numbers are given. What are the 10th and 11th number?

Read more...

By: admin on July 11, 2011, 2:35 p.m.

This sequence is infinite, the first 9 numbers are given. What are the 10th and 11th number?

Read more...

Last edited by: admin on Oct. 31, 2021, 2:54 a.m., edited 1 time in total.

By: Scott on June 14, 2012, 4:18 a.m.

This sequence is infinite, the first 9 numbers are given. What are the 10th and 11th number?

Read more...I seem to have found a different solution to the one you got, but it works with the pattern.

Original pattern:

|10 - 15|25 - 35| 55 - 65 | 85 - 95 | 115 - ? | ? - …

Sub-pattern 1: |10x2-5=15|15x2-5=25|25x2-15=35|35x2-15=55|55x2-45=65|65x2-45=85|85x2-75=95|95x2-75=115|115x2-?=?|

Sub-pattern 2: The pattern doubles then starts by subtracting "5" but then jumps to subtracting 15 after the 5 was subtracted twice. So -5 twice, then -15 twice, then -45 twice, then - 75 twice… Going by this, it seems to triple for the first jump, then triple again, but the jump to 75 is not a triple, so that can't be it.But if you start at 5, then 15, (15 being 5x3), then 45 (which is 5x9) then 75 (which 5x15) you see sub-pattern 2 wich is multiples of 5 increasing by 6 (3,9,15…making the next number in the sequence 21) so using that 5x21 is 105 and if you plug 105 into sub-pattern 1 115x2-105=125 then 125x2-105=145.

But when you put 125,145 into the answer I get it wrong, so there must be another pattern right?

By: Veselovský on June 14, 2012, 8:42 a.m.

But if you start at 5, then 15, (15 being 5x3), then 45 (which is 5x9) then 75 (which 5x15) you see sub-pattern 2 wich is multiples of 5 increasing by 6 (3,9,15…).

But then you forgot 1 as the first multiplier…

5=1*5
15=3*5

45=9

75=15

There is increment of 2 between 1 and 3, not 6.

So neither of your sequences would work.

By: Anna_Drake on May 30, 2014, 5:21 p.m.

i took out the 5 (ie made the sequence 2-3-5…) to look at the numbers without the confusing factor and that really helped. It made the light bulb go off so to speak.

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