Martin used his calculator to work out the value of a number P - Edexcel - GCSE Maths - Question 12 - 2022 - Paper 3

Since Martin wrote down 1.2, this means the actual value of P lies between the closest numbers that would round to 1.2.

The lower bound would be just below 1.2, which is 1.15 (since anything below this would round down to 1.1).

The upper bound would be just below 1.3, which is 1.25 (since anything below this would round down to 1.2).

Thus, the error interval for P is:

$1.15 < P < 1.25$