Ask Singapore Homework?

Upload a photo of a Singapore homework and someone will email you the solution for free.



Question

|
No Answers Yet

Help Leo Ng! Anyone can contribute an answer, even non-tutors.

Answer This Question
Leo Ng
Leo Ng

Secondary 4 chevron_right A Maths chevron_right Malaysia

help me. thanks

Date Posted: 6 months ago
Views: 53
J
J
6 months ago
Let first term be a and common difference be d.

Sum of odd terms: 140

1st + 3th + 5th + 7th + 9th + 11th + 13th
= 140

a + (a+2d) + (a+4d) + (a+6d) + (a+8d) + (a+10d) + (a+12d) = 140

7a + 42d = 140 ①




Sum of even terms: 160

2nd + 4th + 6th + 8th + 10th + 12th + 14th
= 160

a+d + (a+3d) + (a+5d) + (a+7d) + (a+9d) + (a+11d) + (a+13d) = 160

7a + 49d = 160 ②

② - ① :

7d = 20

d = 20/7

7a = 160 - 49(20/7) = 20
a = 20/7