Welcome Guest ( Log In | Register )

Outline · [ Standard ] · Linear+

 help to solve this addmath's question

views
     
TSharuko_08051
post Jan 13 2018, 09:46 PM, updated 7y ago

New Member
*
Newbie
4 posts

Joined: Jan 2018
An arithmetic progression has 10 terms. The first term is 6 and the sum of all the odd terms is 250. Find the common difference.

(come from form 5 chapter 1 progression) mega_shok.gif

help me rclxub.gif

formula
1.Tn=a+(n-1)d
2.Sn=n/2(2a+(n-1)d)
3.Sn=n/2(a+Tn)

a→FIRST TERM
d→COMMON DIFFERENCE

the correct answer is 11
but I find the answer is 22......😢

This post has been edited by haruko_08051: Jan 13 2018, 10:48 PM
CKKwan
post Jan 13 2018, 09:51 PM

Enthusiast
*****
Senior Member
886 posts

Joined: Dec 2004
Just assume that it has 5 terms.

If I remember correctly the formula is 250 = 5/2 (6 + b), where b should be resolved to 94. Common difference for the odd terms are (94 - 6) / 4 = 22

So if there are 10 terms, the common difference should be 11?
TSharuko_08051
post Jan 13 2018, 10:53 PM

New Member
*
Newbie
4 posts

Joined: Jan 2018
QUOTE(CKKwan @ Jan 13 2018, 10:51 PM)
Just assume that it has 5 terms.

If I remember correctly the formula is 250 = 5/2 (6 + b), where b should be resolved to 94. Common difference for the odd terms are (94 - 6) / 4 = 22

So if there are 10 terms, the common difference should be 11?
*
how I can get the answer?? divide by 2?
I want know the reason.....
CKKwan
post Jan 14 2018, 08:21 AM

Enthusiast
*****
Senior Member
886 posts

Joined: Dec 2004
QUOTE(haruko_08051 @ Jan 13 2018, 10:53 PM)
how I can get the answer?? divide by 2?
I want know the reason.....
*
Answer is already mentioned clearly in my earlier post. Ain't gonna help you to do your homework.

BTW, the formula that you have added earlier is correct, but you have chosen the wrong formula for this question.

 

Change to:
| Lo-Fi Version
0.0119sec    0.31    5 queries    GZIP Disabled
Time is now: 28th March 2024 - 05:26 PM