Question

The four numbers in A.P. such that their sum is 50 and greatest of them is '4' times the least then the greatest number is-

• A. 19
• B. 20
• C. 21
• D. None of these

Answer 1

Answer: (B)

20

Answer 2

Let the no. are a – 3d, a – d, a + d, a + 3d

Sum = 50 = 4a

a = $\frac{50}{4}$= $\frac{25}{2}$= 12.5

when a + 3d = 4.(a –3d)

15d = 3a

a = 5d

d = $\frac{a}{5}$= $\frac{25}{10}$= 2.5

Greatest number = a + 3d

= 12.5 + 3. (2.5)

= 12.5 + 7.5

= 20