其它
After every $$3$$ steps that Pip takes forward, he takes $$2$$ steps backwards. Each step is $$1 $$$$\text{m}$$. Pip starts at one end of a $$100$$ $$\text{m}$$ hall. Pip will first reach the other end after~\uline{~~~~~~~~~~}~steps. 
Overseas Competition->Knowledge Point->Word Problem Modules->Periodic Problems->Snail Climbing out of Well Problems
3+2=5, 3-2=1  The pattern: Pip move forward 1m in 5 steps  $$100-3=97$$  $97\times5+3=488$ 