Data Tables: Check the Units, Then Compare

Read the labels before the numbers

A table has two jobs: it stores values and tells us what those values mean. Before calculating, identify the row category, column period and measurement unit. A count of orders is different from an amount in rupees, and a monthly value is different from a two-month total.

The following fictional dataset records orders delivered, not money earned. Each order appears in exactly one branch and one month.

Branch	January orders	February orders
A	80	100
B	120	150
C	100	110

Row totals and column totals answer different questions

To find Branch A's deliveries across both months, stay in row A: 80 + 100 = 180 orders.

To find all January deliveries, stay in the January column: 80 + 120 + 100 = 300 orders. February's total is 100 + 150 + 110 = 360 orders.

The two-month total is 300 + 360 = 660 orders. Cross-check by rows: A gives 180, B gives 270 and C gives 210; 180 + 270 + 210 = 660. These are two ways to count the same orders. Do not add both sets of totals together.

A difference needs a reference; a percentage needs a base

The increase in all deliveries is 360 − 300 = 60 orders. To express growth from January to February, divide by the starting total: 60/300 × 100 = 20%.

Branch B's January deliveries compared with Branch C's January deliveries give 120:100 = 6:5. Both values use the same period and unit, so this comparison is meaningful.

A share answers a different question. Branch A supplied 100 of February's 360 orders. Its February share is 100/360 × 100 = 27 7/9%, about 27.78%. The denominator is the whole February total, not A's January value.

Avoid three common traps

Do not compare January for one branch with February for another unless that is what the question asks. Do not add a total to its own component rows. For growth use the earlier value; for a share use the relevant whole. Keep the final unit: a difference is in orders, a ratio has no unit, and a percentage is per hundred.

Check yourself

1. How many orders did Branch B deliver across the two months?
2. What percentage of all February deliveries came from Branch B? Give an exact value or a stated rounding.
3. What was Branch A's percentage increase from January to February?

Worked answers

1. Read row B: 120 + 150 = 270 orders. This is a two-month branch total, not a February column total.
2. February's whole is 360. B's share is 150/360 × 100 = 41 2/3%, approximately 41.67%. Dividing by 150 would compare B with itself and incorrectly give 100%.
3. A gained 100 − 80 = 20 orders. The starting value is 80, so growth = 20/80 × 100 = 25%. Check: 25% of 80 is 20, and 80 + 20 = 100.

These are original teaching data and practice questions, not questions attributed to an SSC paper.