How many cubes measuring 2 units on one side must be added to a cube measuring 8 units on one side to form a cube measuring 12 units on one side?
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more precisely : ( 1 2 3 − 8 3 ) / 2 3 => 152
Equivalently, we can calculate the number of 1 × 1 × 1 cubes we need to add to a 4 × 4 × 4 cube to form a 6 × 6 × 6 cube, which is equal to 6 3 − 4 3 = 2 1 6 − 6 4 = 1 5 2 .
2x2x2 will have 8 cubes,
8x8x8 will have 512 cubes,
12x12x12 will have 1728 cubes,
so (1728-512)/8=152
8 8 8 = 512
12 12 12 = 1728
1728 - 512 = 1216
2 2 2 = 8
1216 / 8 = 152
Let m be the number of 2 × 2 × 2 cubes needed, then
m = 2 3 1 2 3 − 8 3 = 1 5 2
volume of cube measuring 8 units
v8 = 8³ = 512 cubic units
volume of cube measuring 12 units
v12 = 12³ = 1728 cubic units
difference in volume
v12 - v8 = 1728 - 512 = 1216 cubic units
volume of cube measuring 2 units
v2 = 2³ = 8 cubic units
divide the difference in volume by the volume of cube measuring 2 units
1216/8 = 152 cubes
How to do this if you're lazy and don't have a calculator:
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To form 12x12x12 =1728 minus 8x8x8 =512 divide by 2x2x2=8
n= (12^3)-(8^3)=1216/8 = 152 :)
12x12x12=1728
8x8x8=512
2x2x2=8
1728-512=1216
1216/8=152
2^3=8 8^3=512 12^3=1728 2^3 x + 8^3 = 12^3 8x + 512 = 1728 8x = 1728-512 8x=1216 x=152
(12 12 12)-(8 8 8) = 1216/(2 2 2) = 152
simply 2³x + 8³ = 12³
or x = (12³ - 8³)/2³
x = 152
It's wrong.
1 2 3 − 8 3 = ( 1 2 − 8 ) ( 1 2 2 + ( 1 2 ∗ 8 ) + 8 2 ) = 4 ( 1 4 4 + 9 6 + 6 4 ) = 4 ( 3 0 4 ) = 1 2 1 6
( 1 2 3 − 8 3 ) / 2 3 = 1 2 1 6 / 8 = 1 5 2
You must have put that middle line into a calculator incorrectly.
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8x8x8(single cube)=512 c m 3
let total number of 2 ∗ 2 ∗ 2 cubes be ''a''
then :- 8 a + 5 1 2 = 1 7 2 8
8a=1216
a= 1 5 2