BIDMAS: Watch Out for These Traps!

Don't let these common exam mistakes lose you marks.

Trap 1: The Square Root "Bracket"

A square root symbol \(\sqrt{\dots}\) acts like a bracket. You must finish all operations inside before you find the root.

❌ WRONG \(\sqrt{9 + 16} = 3 + 4 = 7\)
✅ RIGHT \(\sqrt{9 + 16} = \sqrt{25} = 5\)

You cannot "split" a root across addition or subtraction.

Trap 2: Multiplication vs. Division

In BIDMAS, Multiplication and Division have equal priority. You must work from left to right.

❌ WRONG \(12 \div 2 \times 3\)
\(12 \div 6 = 2\)
✅ RIGHT \(12 \div 2 \times 3\)
\(6 \times 3 = 18\)

Many students do the multiplication first just because 'M' comes after 'D' in some versions of the acronym. Always go left-to-right!

Trap 3: Squaring Negative Numbers

This is a major error in algebra and quadratics. Brackets change the result!

❌ Without Brackets \(-5^2 = -25\)
(Only the 5 is squared)
✅ With Brackets \((-5)^2 = 25\)
(The whole \(-5\) is squared)

If you type -5^2 into most scientific calculators, it will give you -25. Always use brackets for negative indices!

Trap 4: Hidden Brackets in Fractions

A fraction bar is a grouping symbol. Treat the numerator and denominator as if they are in brackets.

❌ WRONG \(\frac{10 + 2}{2} = 10 + 1 = 11\)
✅ RIGHT \(\frac{10 + 2}{2} = \frac{12}{2} = 6\)

You cannot cancel terms in a fraction until the addition/subtraction on top and bottom is finished.