Solve the Expression: Finding Substitutable Numbers in 7×4+0÷10

To solve this problem, we need to evaluate the given expression and determine which number can be substituted without affecting the result.

Step 1: Evaluate the original expression
The expression is: $7 \times 4 + 0 : 10$

Following the order of operations (multiplication and division before addition):
• First, calculate $7 \times 4 = 28$
• Next, calculate $0 : 10 = 0$
• Finally, add the results: $28 + 0 = 28$

Therefore, the original expression equals $28$.

Step 2: Analyze which number can be changed
Let's examine each number in the expression:

• The number 7: If we change 7, the product $7 \times 4$ will change, thus changing the final result.
• The number 4: If we change 4, the product $7 \times 4$ will change, thus changing the final result.
• The number 0: If we change 0 to any other number $n$, then $n : 10$ will not equal 0 (for $n \neq 0$), which will change the final result.
• The number 10: This is the divisor in $0 : 10$. Using the property of zero in division, $0$ divided by any non-zero number always equals $0$. Therefore, we could replace 10 with any other non-zero number, and the result would still be $0$.

Step 3: Verify with the property of zero
The key mathematical property here is: $0 \div n = 0$ for any non-zero value of $n$.
So whether we have $0 : 10$, $0 : 5$, $0 : 100$, or $0 : 2$, the result is always $0$.
This means $7 \times 4 + 0 : n = 28 + 0 = 28$ regardless of what non-zero number replaces 10.

Therefore, the number 10 can be substituted without changing the result of the exercise.