It&#x27;s harder because people fail to make relations or don&#x27;t think about how they can simplify a problem. Or big numbers are generally harder for mental math. Either or.<p>Solving 25% of 36 then multiplying by 100 (effectively removing the &quot;%&quot; part of 25%) gets 900. It&#x27;s also a bit indirect, so many people would overlook it (myself included).<p>If you were to ask me what 36 * 25 was in most any other context I&#x27;d do 40 * 25 = 1,000 - 4*25 = 900.<p>Although, thanks to your prompt, I&#x27;m likely to remember to see if I can cheat with percentages. :) Smaller numbers and fractions are more intuitive for me.