First I need to set up an equation [ggfrac]20/n[/ggfrac]=[ggfrac]80/100[/ggfrac] and then use proportional reasoning. I know that 20×4=80, and to keep my ratios equivalent, I need to multiply the numerator and denominator by the same value. This means [i[]n[/i]×4=100, so since 25×4=100 there must be 25 logs in the whole pile.