Help pleaseeeee!

[fluffygirl_27]

1.The cost of making a yd wide around a circular pond 6yds in diameter at £0.35 per sq yd is ???

A=£1.10 B=£5 C=£7.70 D=£9.90 E=£17.60

Thanks

[Qeb2019]

1.The cost of making a yd wide around a circular pond 6yds in diameter at £0.35 per sq yd is ???

A=£1.10 B=£5 C=£7.70 D=£9.90 E=£17.60

Thanks

The wide area is 4x4x3.14-3x3x3.14=7x3.14

The cost is 7x3.14x0.35

Because 3.14x0.35 around 1 so answer is C. Don’t need to do calculation.

Regard

[russet]

I agree with, Qeb2019, but would draw the pond for a child of 11+ age so they can visualise why you are subtracting one area from another. I did not think they did areas of circles or pi at this age. Is it an old book, as it is using yards?

[fluffygirl_27]

1.The cost of making a yd wide around a circular pond 6yds in diameter at £0.35 per sq yd is ???

A=£1.10 B=£5 C=£7.70 D=£9.90 E=£17.60

Thanks

The wide area is 4x4x3.14-3x3x3.14=7x3.14

The cost is 7x3.14x0.35

Because 3.14x0.35 around 1 so answer is C. Don’t need to do calculation.

Regard

Thank you .

[fluffygirl_27]

I agree with, Qeb2019, but would draw the pond for a child of 11+ age so they can visualise why you are subtracting one area from another. I did not think they did areas of circles or pi at this age. Is it an old book, as it is using yards?

I am not sure but thank you

[AdamV]

I know I'm late but I suspect the book is old, or possibly US oriented. Either way I wonder if it is aimed at children at a stage when they are using 22/7 as a "good enough" approximation of pi, in which case the 7's fall out and you end up with 22*.35 so the answer C would be "exact" (based on the initial assumption of pi=22/7), rather than "nearest".