Pythagoras Theorem & Shadow Problems in Reasoning | Direction Sense Part 3

Welcome back to S Chand Academy! In this third part of our RRB NTPC 2026 Reasoning series, we tackle two of the most challenging topics in Direction Sense: Pythagoras Theorem and Shadow-based problems. Whether you are a beginner or looking for advanced shortcuts, this guide will help you solve these questions in seconds.

📺 Watch the Full Lecture

📐 Mastering Pythagoras Theorem in Reasoning

In many competitive exam questions, you are asked to find the "minimum distance" or the "shortest path" between two points. This is where the Pythagoras Theorem comes into play.

The Formula:

Base² + Perpendicular² = Hypotenuse²

Key Triplets to Remember:

Memorizing these common triplets will save you valuable time during the exam [04:14]:

• 3, 4, 5 (3² + 4² = 5²)
• 5, 12, 13 (5² + 12² = 13²)
• 8, 15, 17 (8² + 15² = 17²)

Exam Tip: If the numbers are large (like 50 and 120), remove the zeros, find the triplet (5, 12 → 13), and then add the zero back (130) [15:10].

☀️ Shadow Problems: The Ultimate Concept

Shadow problems often confuse students because they depend on the time of day. Here is the simplified logic:

1. Morning (Sun in the East)

• The sun rises in the East.
• All shadows fall towards the West [17:12].
• If a person is facing North, the shadow is to their Left.
• If facing South, the shadow is to their Right.

2. Evening (Sun in the West)

• The sun sets in the West.
• All shadows fall towards the East [18:26].
• If a person is facing North, the shadow is to their Right.

3. Noon (12:00 PM)

• At exactly 12:00 PM, the sun is directly overhead.
• No shadow is formed to the left or right [33:36].

📝 Practice Challenge

In the video, we discussed a specific clock-based direction question [38:16]:

At 4:30 PM, if the hour hand is pointing South, in which direction will the minute hand be?

Can you solve this? Watch the video for the full explanation and drop your answer in the comments!

📚 Recommended Practice

To score full marks, practice is key. We highly recommend the S Chand Railway Reasoning PYQ Books for the most updated question bank.

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