10.1. Append one digit to the right and one digit to the left of the number 52 so that the resulting number is divisible by 45.

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\text { (5-6 grades) }
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10.1. If a number is divisible by 45, then it is divisible by 5 and by 9. A number is divisible by 5 if and only if it ends in either 0 or 5. A number is divisible by 9 if and only if the sum of its digits is divisible by 9. Now we can easily arrive at the following two solutions to the problem: 2520 and 6525.