Final answer:
The smallest possible value of Liam's number, when rounded to one significant figure as 0.7, is 0.65, and the largest is just below 0.75.
Step-by-step explanation:
If Liam thinks of a number with 2 decimal places and his number is 0.7 when rounded to 1 significant figure, we need to determine the smallest and largest possible values of Liam's number.
When rounding to one significant figure, the smallest value Liam could be thinking of that would round up to 0.7 is 0.65. This is because any number less than 0.65 would round down to 0.6 instead. The largest value he could be thinking of would be anything up to but not including 0.75, because 0.75 would round up to 0.8.