Subject: weight Name: Sarah
Who is asking: Teacher Question: Hi, I was hoping that you could answer these question: A regularsized brick weighs 4 kilograms. How much will a similar toy brick, made of the same material, but all of the same dimensions of which are four times smaller, weigh? The 300metre tall Eiffel tower is made of steel and weighs 8 000 000 kg. An exact replica, made of the same material, weighs 1 kg. How high is the replica Thanks in advance! Hi Sarah,
Imagine that you are going to make the toy brick by cutting up the real brick. First cut off onequarter of the length of the brick. Call this piece slice 1. Slice 1 is onequarter of the whole brick so it weights ^{1}/_{4} x 4 kg.
Next slice off onequarter of the height of slice 1. Call this piece slice 2. Slice 2 weighs onequarter of the weight of slice 1, that is its weight is ^{1}/_{4} x ^{1}/_{4} x 4 kg.
Finally take slice 2 and cut onequarter off its depth. Call this piece slice 3. Slice 3 is onequarter of slice 2 so its weight is ^{1}/_{4} x ^{1}/_{4} x ^{1}/_{4} x 4 kg. Slice 3 is onequarter as long, onequarter as high and onequarter as deep as the original brick so this is the toy brick you wanted. For the second problem, suppose that the replica is ^{1}/_{a} times the height of the real tower. Now can you do the second problem? Penny
