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Question

hi! can help us with this qn? tq!

.

Our answer was different from the answer provided and we’re wondering how they derive at ans: 520. 

Source: Methodist Girls’ School Primary

Answer

(40/5) x (30/3) x (15/3) = 400
(39/3) x (30/3) x (5/5) = 130
400 + 130 = 530

or

40/5 = 8
30/3 = 10
(20 – 5)/3 = 5 (this is to fill the carton up to 15 cm leaving 5 cm so as to fit the greatest number of cuboids into it)
8 x 10 x 5 = 400
5/5 = 1
40/3 = 13R3
30/3 = 10
1 x 13 x 10 = 130
400 + 130 = 530

Ans : 530 cuboids.

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Correct ans is not 520.

I hv pm you the solution.

 

cheers.

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Why not post it here so all can benefit?

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  40 cm 30 cm 20 cm Total
5 cm along 40 cm side 40 ÷ 5 = 8 30 ÷ 3 = 10 20 ÷ 3 = 6 r 2 8 × 10 × 6 = 480
5 cm along 30 cm side 40 ÷ 3 = 13 r 1 30 ÷ 5 = 6 20 ÷ 3 = 6 r 2 13 × 6 × 6 = 468
5 cm along 20 cm side 40 ÷ 3 = 13 r 1 30 ÷ 3 = 10 20 ÷ 5 = 4 13 × 10 × 4 = 520
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