Question

(i) How many numbers are there between 99 and 1000 having 7 in the units place?

Answer 1

Answer:

90

Step-by-step explanation:

Numbers between 99 & 1000 having 7 in unit place would be

107 , 117 , 127 ........................, 987 , 997

This is an AP where

a = 107  

d = 117-107 = 10

Last number = 997

n = to be find

L = a + (n-1) d      

997 = 107 + (n-1) * 10

890 = (n-1) * 10

89 = n-1

n = 90

so 90 numbers will be there between 99 & 1000 having 7 in units place