+11912 Sana made a cuboid of plasticine of sides 5cm,2cm,5cm . How many such cuboids will need to form a cube?
if u can explain this using a very easy method then i'd be really greatful!
+118608
Hi Rosala,
The lowest common multiple of 2 and 5 is 10. So I think the cube would have to have side length 10cm
If you let the front of the little rectangular prism (you call that a cuboid) be 2cm by 5cm
2*5=10 and 5*2=10 so there will be 5*2=10 0f these making up the front of the cube
The little boxes go back 5cm so you will need to double this to get 10 cm.
So the answer must be 5*2*2=20 little cuboids.
I'll see if I can draw it.
+118608
Hi Rosala,
The lowest common multiple of 2 and 5 is 10. So I think the cube would have to have side length 10cm
If you let the front of the little rectangular prism (you call that a cuboid) be 2cm by 5cm
2*5=10 and 5*2=10 so there will be 5*2=10 0f these making up the front of the cube
The little boxes go back 5cm so you will need to double this to get 10 cm.
So the answer must be 5*2*2=20 little cuboids.
I'll see if I can draw it.
+128633 Look at Melody's diagram, rosala. Note that the pink cuboid measures 5cm by 5 cm on one outside face. And Melody has noted that if we put a similar one underneath it and stack two more similar ones beside these two, we will have a face of a cube that will be 10 cm wide and 10 cm "tall." Now, look at the other side of the cuboid. It measures 2cm x 5 cm. And if we stack two of these together we will have the correct height of 10 cm. And if we do this 5 times, the width of the cube "facing us" will be 10 and its height will be 10 !!!
So the cube will neasure 10 x 10 x 10......
Does that nake sense?? (This is a tough one to see !!! Melody solved it very nicely, using the prime factors of 10.)
Just for the heck of it, try this with another number, say 14, whose prime factors are 2 and 7 !!!!! It will work the same way !!!!
