Question 74

What percentage of numbers from 1 to 80 have 1 or 9 in the units digit?

Solution

From 1 to 9 each of 1 and 9 comes once at the units digit i.e 2 times(1 or 9)
From 10 to 19 each of 1 and 9 comes once at the units digit i.e 2 times
Similarly till 80 they come once for every ten numbers and so
Total=8*2=16 times
Total numbers =80
Percentage=((16)/(80))*100
=20%

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