Can someone please see where my mistakes are for the following measurement questions, thank you in advance

[kpad5991]

My working out is below the question and the actual solution is in bold.

 

[Otis]

Hi kpad. For Question (1), I got your answer, too.

Some of your rounding is off, yet your final answer matches mine.

You'd written:

30×15 + 30×11.66 = 799.86

That's actually 799.80

I'd rounded intermediate results to three decimal places, rounding to one decimal place only at the end.

I don't have time to check your work on the other three questions right now, but perhaps your answers for those are correct, too.

?

 

[Harry_the_cat]

Q3 The height from dot to dot is 15cm, so the height of the big pyramid is 23 cm. You've taken the whole height to be 15cm (in which case your answer is correct). I agree that the diagram is a little unclear.

Q4. I agree with your answer. I would say they have put r (which is the usual symbol for radius) in the wrong spot in the diagram. If you use 11 rather than 3, you get the answer they got.

Q1. I agree with your answer too.

I'll check Q2 a bit later.

 

[Dr.Peterson]

For #2, you are misinterpreting the shape of the top. Note which sides are marked as perpendicular; the perpendicular height is 5.9 mm.

 

[kpad5991]

Tha

For #2, you are misinterpreting the shape of the top. Note which sides are marked as perpendicular; the perpendicular height is 5.9 mm.

View attachment 28808

I worked it out and the Sa top and bottom (which are trapezium+ is 38.94 mm^2

When I added it all up it gave me 480.4 mm^2. The answer says is 512.0 mm^2

 

[Dr.Peterson]

Tha

I worked it out and the Sa top and bottom (which are trapezium+ is 38.94 mm^2

When I added it all up it gave me 480.4 mm^2. The answer says is 512.0 mm^2

Did you also correct the area of the left side? It is not the same as the right side! You assumed that the top is an isosceles trapezoid, which it is not.

 

[kpad5991]

Did you also correct the area of the left side? It is not the same as the right side! You assumed that the top is an isosceles trapezoid, which it is not.

I still didn’t get 512.0 mm^2

SA front = 64.4
SA back = 148.1
SA rhs = 95
SA lhs = 163.8 (not too sure if this is correct)
SA top = 38.9
SA bottom = 32.1

total = 542.3

the answer is 512.0 (how??)

 

[Dr.Peterson]

I still didn’t get 512.0 mm^2

SA front = 64.4
SA back = 148.1
SA rhs = 95
SA lhs = 163.8 (not too sure if this is correct)
SA top = 38.9
SA bottom = 32.1

total = 542.3

the answer is 512.0 (how??)

Please show your work for LHS, top, and bottom. How do you get the top and bottom different? We may still be interpreting something differently, but I do get their answer.

 

[kpad5991]

Please show your work for LHS, top, and bottom. How do you get the top and bottom different? We may still be interpreting something differently, but I do get their answer.

I worked it out in the end.