WAEC Mathematics 2014 Paper

Concept:Leading zeros are not significant. Only nonzero digits and trailing zeros after a decimal point are counted for significant figures.Explanation:Write $0.0033780$ in scientific notation:$$0.0033780 = 3.3780 \times 10^{-3}$$To round to 3 significant figures, look at the fourth significant digit, which is $8$.Since $8 \ge 5$, round $3.378$ up to $3.38$.Now convert back to ordinary notation:$$3.38 \times 10^{-3} = 0.00338$$The three zeros before the digit $3$ are not significant, so they remain in the decimal value.Thus the value of $0.0033780$ correct to 3 significant figures is $0.00338$.Answer:$0.00338$