The average of first three out of four numbers is 18. The average of the last three numbers is 14. The sum of the first and last number is…

Let the four numbers be m, n, o, p.

From the given data,

Average of the first three out of four numbers is 18

⇒ (m + n + o) /3 = 18

⇒ Sum of the first three numbers (m + n + o) = 54 ----(1)

Also given that average of the last three numbers = 14

⇒ (n + o + p)/3 = 14

⇒ Sum of the last three numbers (n + o + p) = 42 ---- (2)

Subtract equation (2) from equation (1), we get

⇒ m - p = 12 ----(3)

Also given that sum of the first and last number = 16

⇒ m + p = 16 ----(4)

Subtract equation (4) from equation (3), we get

⇒ -2p = -4

∴ p = 2

∴ Last number p = 2