GATE Electrical Engineering (EE) 2020 Solved Paper

Question : 8 of 65

Marks: +1, -0

A four-digit integer number from

1001-9999

, the digit group '37' (in the same sequence) appears times.

Solution:

\X↙{↓↙{9}}\;\;\X↙{↓↙{10}}\;\;\;3\;7=9× 10 =90

\X↙{↓↙{9}}\;\;\;3\;7\;\;\X↙{↓↙{10}}\=90× 10 =90

3\;7\;\;\X↙{↓↙{10}}\;\;\;\X↙{↓↙{10}}\=10× 10 =100

= 90 + 90 + 100 = 280

X 3 7 X and X X 3 7 will repeat twice

= 280-1 = 279

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