a backyard was measured with a degree of accuracy to the nearest 2m; 20m × 30m. what is the largest possible area of the backyard to the nearest m2? 651 m2

We determine the largest possible area of the backyard by multiplying the length and width using the greatest values for each dimensions which is 22 for the length and 32 for the width, or vice versa. 
                                          Area = (32 m) x (22 m)
                                                    = 704 m²
Thus, the answer is 704 m².
Note: The answer given above was obtained by multiplying 31m by 21 m. 

It’s b because vpt is the whole triangle and ptc isn’t