In rounding or truncation of a number to n decimal places, the original is replaced by a number with just n digits after the decimal point. When the rounding takes place to the left of the decimal point, a phrase such as ‘to the nearest 10’ or ‘to the nearest 1000’ is used. To say that a = 1.9 to 1 decimal place means that the exact value of a becomes 1.9 after rounding to 1 decimal place, and so 1.85 ≤ a < 1.95. ‘Decimal places’ is often abbreviated to ‘dp’.