A square triangle represents two natural numbers. When one number is divided by another, the quotient is greater than nine. What's the smallest number?

Square stands for dividend, triangle stands for divisor, quotient is 9, and remainder is 4.

According to the fact that the divisor cannot be less than the remainder, the divisor is at least 5.

According to the relationship among remainder, quotient, divisor and dividend, quotient x divisor+remainder = dividend.

So 5x9+4=45+4=49.

So the minimum dividend is 49.