A rain gauge recorded 3.6 mm of rain on Monday, 0.85 mm on Tuesday and none on Wednesday. By Thursday evening the four-day total stood at 7.5 mm. How much rain fell on Thursday?

To the LEFT of the decimal point: ones, tens, hundreds — each place is **10 times** bigger than the one to its right. To the RIGHT of the decimal point, the same rule continues — each place is **10 times smaller** than the one to its left. So:

- 1st place after the point: tenths (1/10)
- 2nd place: hundredths (1/100)
- 3rd place: thousandths (1/1000)

The decimal $23.456=2\times 10+3\times 1+4\times (1/10)+5\times (1/100)+6\times (1/1000)$.