How many three-digit positive integers have their hundreds, tens and units digits in ascending order?

Options
- 70
- 77
- 84
- 91

CORRECT ANSWER : 84

Discussion Board
answer detail

100s
123, 124, 125, 126, 127, 128, 129,
134,135,136,137,138,139
145,146,147,148,149
156,157,158,159
167,168,169
178,179,
189
Total = 7+6+5+4+3+2+1 = 28 numbers

For 200s doing similar total = 6+5+4+3+2+1= 21 numbers
for 300s 5+4+3+2+1 = 15 numbers
for 400s 4+3+2+1 = 10 numbers
for 500s 3+2+1 =6 numbers
for 600s 2+1 = 3 numbers
for 700 1 number (789)
total = 84

Zeki Bulbul 02-5-2022 10:53 PM

doubt

x2

doubtx2 03-11-2020 06:40 PM

doubt

I want more explanation

priya 09-2-2014 02:54 AM

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