Start here · the first lesson of Net displacement / final direction
Net displacement / final direction
Direction Sense · for IPMAT Indore, IPMAT Rohtak and JIPMAT
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The idea
A person walks, turns and walks again, or a list of statements places points relative to one another ("F is 15 m north of M"). Questions ask the distance from the start, the direction of the end point (or of one point from another), the final heading, or whether two statements are enough. Every Rohtak and JIPMAT LR paper from 2019 to 2026 has one or two such items.
Textbook vs exam method
Textbook method
Put the start at the origin with north up. Convert every leg into an east-west step (+x east) and a north-south step (+y north), keeping track of the heading after each turn. The final point (x, y) gives the distance and the direction: north/south from the sign of y, east/west from the sign of x.
Exam method
- Heading first, distance second. Write the heading before each leg: S, then right = W, then left = S...
- Two totals. Add the east legs and subtract the west legs; do the same north-south. Cancelling legs often leave a straight line (Rohtak 2020: 140 m).
- Pythagorean triples. 3-4-5, 6-8-10, 5-12-13, 8-15-17, 7-24-25: if the totals are a triple, the answer is immediate.
- Relative statements. pick the most connected point as the origin and place the others one by one; for coded statements decode the rule first (sum, average or product of the two numbers).
- Direction of X from Y. compute X minus Y, never the reverse.
- Clock face as a compass. if the 3 points north-west, every hour mark is 30° further clockwise; opposite marks (3 and 9) point in opposite directions.