150 x 100 = 15000
150 times 100 is 15000. Add two zeros to 150. The same answer comes out of 15 times 1000, and the near miss people land on is 1500. Working and calculator below.
150 × 100 = 15,000
Adding 150 to itself 100 times gives the same answer.
The working
Two zeros onto 150 gives 15000. Another way to read it: 150 is one and a half hundreds, so the answer is one and a half ten thousands. Checking backwards, 15000 divided by 100 = 150 and 15000 divided by 150 = 100.
The same 15000 from a different pair
15 x 1000 also equals 15000. That is not a coincidence. 150 x 100 is the same as (15 x 10) x 100, and a factor of ten can move from one side to the other without changing the product, so 150 x 100 and 15 x 1000 are one sum wearing two outfits. Memorise either and you have both.
The factor of ten people actually get wrong
The common slip is losing a zero somewhere in the middle:
- 15 x 100 = 1500
- 150 x 10 = 1500
- 150 x 100 = 15000
1500 and 15000 look alike at a glance and are ten times apart. Count the zeros in both inputs before you accept an answer: 150 has one zero, 100 has two, so the answer ends in three.
More pairs of this size sit on the multiplication answers hub.