1. I read as many pages as are required.
这句中没有省略，其中的 as 是关系代词，引导定语从句（as are required）。句意为：要求读多少页我就读多少页。
2. The girl are as busy with their work as bees.
原句有笔误，girs 应为 girls。此句可认为 bees 之省略了系动词 are。as…as 结构的基本用法，句意为：姑娘们的工作十分忙。注意句中的 as busy as bees 为习语，意思是“非常忙”。
3. Work is as necessary for peace of mind as for health of body.
此句若要说有所省略，可认为是Work is as necessary for peace of mind as it is necessary for health of body 的省略，其意为：工作不仅对于心灵的平静是必要的，对于身体的健康也是必要的。
4. Buying a new bike is sometimes as cheap as repairing the old one is.
不知你的句子出处何处。感觉句末的 is 是多余的。句子大意为：买一辆新的自行车有时跟修理旧自行车一样便宜。