Solve the following multiplication and addition problems, including a word problem about fan blades.

Step 1: Fill in the boxes. The boxes represent multiplication tables.

Row 1 (2 times table): $2, 4, 6, 8, 10, 12, 14$

Row 2 (5 times table): $5, 10, 15, 20, 25, 30, 35$

Row 3 (10 times table): $10, 20, 30, 40, 50, 60, 70$

Step 2: Write the repeated additions as multiplication.

• $3 + 3 + 3 + 3 = 4 \times 3$
• $5 + 5 + 5 = 3 \times 5$

Step 3: Write the multiplications as repeated addition.

• $3 \times 4 = 3 + 3 + 3 + 3$
• $4 \times 6 = 4 + 4 + 4 + 4 + 4 + 4$
• $1 \times 7 = 1 + 1 + 1 + 1 + 1 + 1 + 1$
• $4 \times 5 = 4 + 4 + 4 + 4 + 4$

Step 4: Fill in the blanks.

• $4 \times 2 = \boxed{8}$
• $3 \times 8 = \boxed{24}$
• $4 \times 7 = \boxed{28}$
• $2 \times 9 = \boxed{18}$
• $2 \times 7 = \boxed{14}$
• $5 \times 6 = \boxed{30}$

Step 5: Add by using multiplication table.

• $2 + 2 + 2 + 2 + 2 = 5 \times 2 = \boxed{10}$
• $4 + 4 + 4 + 4 + 4 + 4 = 6 \times 4 = \boxed{24}$
• $3 + 3 + 3 + 3 = 4 \times 3 = \boxed{12}$
• $5 + 5 + 5 = 3 \times 5 = \boxed{15}$

Step 6: Solve the word problem. A fan has three blades. A room has four fans. To find the total number of fan-blades, multiply the number of blades per fan by the number of fans. $3 \times 4 = \boxed{12}$