Step 1: Write 125×25 into the vertical multiplication line, and pay attention to the right alignment of single digits. As shown in the figure:

Step 2: Calculate 5× 125, and the result is 625, which is written vertically (since 5 is the single digit of the multiplier "25", the result needs to be aligned with single digits). As shown in the figure:

Step 3: Calculate 2× 125, and the result is 250 (because 2 is the decimal number of the multiplier "25", the result needs to be aligned with this decimal number). As shown in the figure:

Step 4: Add "0" to the single digit of the result obtained in step 3 (the actual calculation can be omitted, and it is added here for convenience of explanation). As shown in the figure:

Step 5: Calculate 625+2500 and get the result. Namely: 125×25=3 125. As shown in the figure:

Three-digit times two-digit correlation method:

1, estimation method: use rounding method to estimate.

2. Calculate three digits multiplied by two digits vertically. Note that the end of the product in the second step is written in ten digits.

3. Multiply three digits with zero in the middle or at the end of the factor by two digits.

Multiply the middle by a factor of 0; If there is a zero at the end, align the last digit of the number in front of the two factors, multiply it by the number in front of zero, and then it will return to zero, and several zeros will return to several zeros.