Addition: Addition of 2-digit and 1-digit numbers with the regrouping of tens

To solve the problem, we will determine the value of $\triangle$ in the equation $5 + \triangle = 10$.

Here are the steps:

• Step 1: Write down the original equation:

$5 + \triangle = 10$

• Step 2: Isolate $\triangle$ by subtracting $5$ from both sides of the equation:

$\triangle = 10 - 5$

• Step 3: Calculate the result:

$\triangle = 5$

Thus, the numerical value of the triangle symbol is $5$.

Therefore, the solution to the problem is $5$.

To determine the value of the triangle, we begin with the equation given:

$\triangle + 7 = 10$

We want to isolate $\triangle$. To do so, we subtract 7 from both sides of the equation:

$\triangle + 7 - 7 = 10 - 7$

This simplifies to:

$\triangle = 3$

Thus, the value of the triangle is $3$.

To solve this problem, we'll follow these steps:

• Step 1: Set up the equation.
• Step 2: Isolate the triangle symbol using subtraction.
• Step 3: Calculate the numerical value of the triangle.

Now, let's work through each step:

Step 1: Set up the equation:

We start with the equation $8 + \triangle = 30$.

Step 2: Isolate the triangle symbol:

To find $\triangle$, we subtract $8$ from both sides of the equation:

$\triangle = 30 - 8$

Step 3: Calculate the numerical value of the triangle:

Performing the subtraction gives us:

$\triangle = 22$

Therefore, the solution to the problem is $\triangle = 22$.

To solve this problem, we'll follow these steps:

• Recognize the format of the provided equation.
• Apply the appropriate arithmetic operation to isolate $\triangle$.
• Perform the necessary calculations.

Now, let's work through each step:
Step 1: The given equation is $78 + \triangle = 80$. We are tasked with finding the value of $\triangle$.
Step 2: To find $\triangle$, rearrange the equation to solve for $\triangle$:
$\triangle = 80 - 78$.
Step 3: Subtract the known value from the total to isolate $\triangle$:
$\triangle = 80 - 78 = 2$.

Hence, the solution to the problem is $\triangle = 2$.

To solve this problem, we'll follow these steps:

• Step 1: Identify the given information

• Step 2: Rearrange the equation to solve for $\triangle$

• Step 3: Perform the subtraction to find $\triangle$

Now, let's work through each step:
Step 1: The problem gives us the equation $8 + \triangle = 40$. We need to find the value of $\triangle$.
Step 2: To isolate $\triangle$, we subtract 8 from both sides of the equation: $\triangle = 40 - 8$.
Step 3: Perform the subtraction, $40 - 8 = 32$.

Therefore, the solution to the problem is $\triangle = 32$.

To solve this problem, we'll follow these steps:

• Step 1: Rewrite the given equation by subtracting 79 from both sides.
• Step 2: Simplify the result to isolate and determine the value of the triangle $(\triangle)$.

Now, let's work through each step:
Step 1: We start with the equation $\triangle + 79 = 80$. To isolate $\triangle$, subtract 79 from both sides:
$\triangle + 79 - 79 = 80 - 79$.

Step 2: Simplify the result:
$\triangle = 1$.

Therefore, the numerical value of the triangle is $\triangle = 1$. This corresponds with choice 3.

To determine the value of the triangle, we will solve the equation $41 + \triangle = 50$.

Let's solve it step by step:

• Step 1: Start with the equation: $41 + \triangle = 50$.
• Step 2: To isolate $\triangle$, subtract 41 from both sides:
• Step 3: $41 + \triangle - 41 = 50 - 41$.
• Step 4: This simplifies to $\triangle = 9$.

Therefore, the solution to the problem is $\triangle = 9$.

To solve the equation $33 + \triangle = 40$, we will follow these steps:

• Step 1: Write down the equation: $33 + \triangle = 40$.
• Step 2: Subtract 33 from both sides to isolate $\triangle$:
• $\triangle = 40 - 33$.
• Step 3: Perform the subtraction: $40 - 33 = 7$.

Therefore, the numerical value of the triangle $\triangle$ is $7$.

Accordingly, the correct answer choice is $7$, which matches choice 4.

To solve this problem, we'll use basic arithmetic involving subtraction:

• Step 1: Understand the equation $56 + \triangle = 60$.
• Step 2: To isolate $\triangle$, subtract 56 from 60.
• Step 3: Calculate $60 - 56$, which gives us the value of $\triangle$.

Now, let's work through each step:

Step 1: We recognize that we need $\triangle$ such that $56 + \triangle = 60$.

Step 2: Subtract 56 from 60: $60 - 56$.

Step 3: Perform the calculation: $60 - 56 = 4$.

Therefore, the value of the triangle $\triangle$ is $4$.