But that speed is exactly the problem. Solved carelessly, the puzzle produces wildly wrong answers like 1010 or 80. Solved correctly, using one basic rule from grade-school math, it reveals a clean, logical result: Sarah is 20 years old.

The Puzzle That Trips Everyone Up

The expression is written out plainly: 110 – 10 x 10 + 10. At a glance, it seems to invite a quick left-to-right calculation, which is exactly why so many people stumble on it.

The puzzle isn’t about clever wordplay or hidden meaning. It’s a straightforward test of whether the solver remembers the standard order of operations, the rule that governs which calculations happen first in any math expression.

Solving It Step by Step

The order of operations states that multiplication and division must always be completed before addition and subtraction. When operations share the same priority level, they are calculated from left to right.

Applying that rule here, the first task is to scan the expression for multiplication or division. The only one present is 10 x 10, which equals 100. Substituting that back in turns the expression into 110 – 100 + 10.

From there, only subtraction and addition remain, and since they carry equal priority, they’re solved left to right. First comes 110 – 100, which equals 10. The expression simplifies to 10 + 10.

The final step is simple addition: 10 plus 10 equals 20. That is the correct, final answer to the puzzle. Sarah is 20 years old.

Why So Many Get It Wrong

The most common error comes from solving the expression in a straight line, left to right, ignoring the multiplication rule entirely. Done that way, 110 – 10 is calculated first, giving 100. Then 100 x 10 is calculated next, producing 1000. Adding the final 10 brings the total to 1010, an answer that’s far removed from the correct one.

A second mistake involves doing the addition at the end before anything else. Some solvers add 10 + 10 first to get 20, then subtract that result from 100, arriving at an answer that is also incorrect.

Both mistakes come from the same root cause: skipping or misapplying the order of operations. The rule exists precisely so that any expression, no matter who solves it or where, produces one single correct answer rather than several competing guesses.

Working through 110 – 10 x 10 + 10 the proper way, multiplication first, then left-to-right subtraction and addition, leaves no room for ambiguity. The math checks out cleanly, and Sarah’s age comes out to a tidy 20.