Question

if the 11th term of an ap is 44 and 16th term is 19, find the 20th term and the ap.

Answer 1

Answer:

tn=a+(n-1)d

t44 = a + (44-1)d

=> t44 = a + 43d = 44 -------------------------(1)

t16 = a +(16-1)d

=> t16 = a + 15d = 19 ---------------------------(2)

Subtract (1) - (2)

=> a + 43d - a - 15d = 44-19

=> 43d - 15d =25

=>28d = 25

=> d => 25/28

substituting d in equation (2)

=> a + 15(25/28) = 19

=> a = 19 - 15(0.8929)

=> a = 19 - 13.39

=> a = 5.607

t20 = 5.607 + (19)25/28

t20 = 5.607 + 16.964

t20 = 22.571