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Free GMAT Graphics Interpretation Practice Question

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Quarterly electricity output in gigawatt-hours for five plantsGrid of output in gigawatt-hours. Rows are five plants; columns are quarters Q1 to Q4. Every cell shows its value.Q1Q2Q3Q4Riverbend300310305308Highland180120140135Coastal7010011030Summit400395390385Delta605514595

The heat map below shows electricity output, in gigawatt-hours, for each of five power plants over four quarters (Q1 through Q4) of last year: Riverbend, Highland, Coastal, Summit, and Delta. Each cell is labeled with its value. Select from each drop-down menu to complete the statement so that it is most accurate according to the data shown.

From one quarter to the very next quarter, the plant that suffered the largest single-quarter decrease in output was , a drop of gigawatt-hours.

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Answer & Explanation

Correct answer

1: Coastal · 2: 80

The question asks for the largest fall from one quarter to the very next, which is the most negative change between two adjacent cells in a plant's row, not the largest output anywhere and not the largest swing regardless of direction.

Riverbend barely moves, around 300 to 310 across the year, with no drop bigger than 5. Highland falls 60 from Q1 to Q2, its sharpest drop. Coastal runs 70, 100, 110, 30, and that last step, Q3 to Q4, is a fall of 80. Summit sits near 400 but drifts down only 5 a quarter. Delta goes 60, 55, 145, 95, so its biggest fall is 50, from Q3 to Q4. The largest single-quarter decrease is Coastal's 80.

Two traps pull the eye away. Summit has the largest outputs, near 400 every quarter, so it looks important, but its quarter-to-quarter drops are only 5; a big level is not a big change. And Delta posts the biggest single-quarter swing on the whole grid, a jump of 90 from Q2 to Q3, so a solver scanning for the largest movement lands on Delta, but 90 is a rise, not a drop, and the question asks for a decrease. Resolve the direction first: among the falls, Coastal's 80 is the largest.