Solution:
10th term = 41
18th term = 73
a + 9 d = 41 ------- (1)
a + 17 d = 73 ------- (2)
Subtracting the second equation from first equation
a + 9 d = 41
a + 17 d = 73
(-) (-) (-)
-------------------
-8 d = -32
d = (-32)/(-8)
d = 4
Substitute d = 4 in the first equation
a + 9 (4) = 41
a + 36 = 41
a = 41 – 36
a = 5
Now we have to find 27th term
tn = a + (n - 1) d
= 5 + (27-1) 4
= 5 + 26 (4)
= 5 + 104
= 109