Data Interpretation (Tables)

A DI set is a table plus four or five questions. The maths is easy — addition, average, ratio, percentage. Marks go on reading the wrong row or column, and on choosing the wrong base for a percentage.

The four things asked:

1. Total of a row or a column. Just add — and do not drop the "others" head.
2. Average = total ÷ number of entries. Count the entries, do not assume five.
3. Ratio of two entries — divide both by their HCF, and keep the order the question asked for.
4. Percentage. Two different kinds, and this is where the topic is won:

• Share of the total: part × 100 ÷ total. The base is the total.
• Increase or decrease: (new − old) × 100 ÷ old. The base is the earlier value, never the later one.

The single most common mistake is using the wrong base for a percentage increase. "By what percent did production rise from 250 to 300?" is 50 × 100/250 = 20%, not 50 × 100/300 = 16.67%. Both numbers are printed as options. Remember: a change is always measured against where you started.

Before computing, underline the row name and the year in the question. Almost every wrong answer in DI comes from the right calculation on the wrong number.

average = total/number of entries · share% = part × 100/total · increase% = (new − old) × 100/old · ratio: divide both by the HCF

A table shows production of 250 lakh tonnes in 2019 and 300 lakh tonnes in 2022. By what percent did it increase? → Increase = 300 − 250 = 50, taken on the earlier value: 50 × 100 ÷ 250 = 20%. Sanity check: 50 is a fifth of 250, and a fifth is 20%. Using 300 as the base would give 16.67%, which answers a different question — "by what percent was the 2019 figure lower than 2022?"