1
Identify values - 2019 sales = 40 lakhs, 2022 sales = 100 lakhs
2
Apply formula - Percentage increase = [(100-40)/40] × 100
3
Calculate - (60/40) × 100 = 1.5 × 100 = 150%
Answer: 150% increase
Worked Example 2: A bar chart shows production of three items P, Q, R in 2021: P=120, Q=80, R=200. Find the ratio of P to total production.
1
Find total production - 120 + 80 + 200 = 400
2
Find ratio - P : Total = 120 : 400
3
Simplify - Divide by HCF (40) = 3 : 10
Answer: 3:10
Common Mistake #1: Students often confuse the base value in percentage calculations. Always remember - percentage increase/decrease is calculated with respect to the original (earlier) value, not the final value. This is the most frequent error in bar chart questions.
Another common error is misreading the scale or units. Always check if values are in units, tens, hundreds, thousands, or lakhs. Missing a zero in calculation can cost marks