Find the four numbers in A.P. whose sum is 50 and in which the greatest number is 4 times the least.
Let the four numbers be (a – 3d), (a – d), (a + d) and (a + 3d)
a – 3d + a – d + a + d + a + 3d = 50
4a = 50
a = 
According to question,
(a + 3d) = 4(a – 3d)
a + 3d = 4a – 12d
3a = 15d
5d = 
d = 
Therefore,
a – 3d = 
- 
= 5
a – d = 
- 
= 10
a + d = 
+ 
= 15
a + 3d = 
+ 
= 20
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