Question

select the two multiplication problems that show correct calculations using the standard algorithm.
25 20
×13 ×12
75 40
+250 +200

14 13
×14 ×23
46 39
+140 +23

Explanation:

Step1: Analyze \( 25 \times 13 \)

The standard algorithm for multiplication: first multiply \( 25 \times 3 = 75 \), then multiply \( 25 \times 10 = 250 \) (note the 1 in 13 is in the tens place, so we add a zero at the end), then add \( 75 + 250 = 325 \). The calculation here is correct.

Step2: Analyze \( 20 \times 12 \)

Using the standard algorithm: \( 20 \times 2 = 40 \), \( 20 \times 10 = 200 \), then \( 40 + 200 = 240 \). The calculation here is correct.

Step3: Analyze \( 14 \times 14 \)

First, \( 14 \times 4 = 56 \), but the problem shows 46, which is incorrect. So this is wrong.

Step4: Analyze \( 13 \times 23 \)

First, \( 13 \times 3 = 39 \), then \( 13 \times 20 = 260 \) (not 23, since 2 is in the tens place, we should have 260). So this is wrong.

Answer:

The two correct ones are the first (\( 25 \times 13 \)) and the second (\( 20 \times 12 \)) problems. So the checkboxes for \( 25 \times 13 \) and \( 20 \times 12 \) should be selected.