80% of what number is 90? Choose matching definition square 100 square 80

To solve this problem, we need to find the number that, when multiplied by 80%, equals 90.<br /><br />Let's represent the unknown number as $x$.<br /><br />We can set up the equation:<br />\[ 0.8x = 90 \]<br /><br />To solve for $x$, we need to divide both sides of the equation by 0.8:<br />\[ x = \frac{90}{0.8} \]<br /><br />Now, let's calculate the value of $x$:<br />\[ x = 112.5 \]<br /><br />Therefore, the number we are looking for is 112.5.<br /><br />So, the correct answer is:<br />\[ \boxed{112.5} \]