BDMO National Primary 2018/6
- nahin munkar
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An even number is called a ‘good’ even number if its first and last digits are also an even number. How many $3$-digit ‘good’ even numbers are there? Try to find their number without writing all such number!
# Mathematicians stand on each other's shoulders. ~ Carl Friedrich Gauss
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Re: BDMO National Primary 2018/6
For the first digit there are $4$ options ($2,4,6,8$).
For the middle digit there are $10$ options($0,1,2,3,4,5,6,7,8,9$).
For the last digit there are $5$ options($0,2,4,6,8$)
So there are total $4×10×5$ or $200$ such even numbers.
For the middle digit there are $10$ options($0,1,2,3,4,5,6,7,8,9$).
For the last digit there are $5$ options($0,2,4,6,8$)
So there are total $4×10×5$ or $200$ such even numbers.