Upper Bound of H in GCSE Maths

[tomtomtom1]

Hi all

I have another upper/low bound question, i have attached the question to this thread.

The bit i am having trouble with is part (II) i.e. calculate the upper bound of H.

I attempted this and got: -

(24.45^2)/(2*9.85) = 30.34530457

H = 30.3 (3 sig fig)

The problem is that my answer differs from the model answer shown in the attachment, the reason why i did what i did was because the question stated find the Upper Bound of H, so i thought i need to use the upper bound of v & g to calculate the upper bound of H, why am i incorrect?

Thanks

 

[BvU]

The upper bound of 1/g is found when the lower bound of g is used.

Same thing with subtraction: upper bound of 1.7 - 1.2 is 1.75 - 1.15 = 0.6.
And lower bound is 0.4. With your method upper and lower bound would be the same as the calculated difference itself...