NCERT Solutions Ganita Prakash Chapter 10 In-text Questions — Bela’s Building of Fun
Book page 243 Updated on2026-09-05
Q1.
Can there be a number less than 0? Can you think of any ways to have less than 0 of something?
Answer
Yes. A number less than 0 makes perfect sense the moment we start counting in two opposite directions from a starting mark.
Floors of a building — the ground floor is 0, and the basement floors below it are – 1, – 2, – 3, …
Temperature — in Leh or Drass the thermometer often shows – 4 °C, that is 4 degrees below the freezing point of water.
Money — if you have ₹100 and you owe a shopkeeper ₹150, you are ₹50 short. Your balance is – ₹50.
Sea level — the shore of the Dead Sea is about 430 m below sea level, so its height is – 430 m.
A lift in a mine — a level 90 m below the ground is marked – 90 m.
Why it works: zero here does not mean ‘nothing’. It is a reference point — the ground floor, the freezing point, the sea level. Once we fix a zero, we can go both above it (positive) and below it (negative).
Q2.
Observe that some of the floors in the ‘Building of Fun’ are below the ground. What are the shops that you find on these floors? What is there on the ground floor?
Answer
Look at the picture of Bela's Building of Fun. Below the ground there are five floors:
Toy Store — the first floor below the ground
Video Games — the second floor below
Cinema — the third floor below
Ghost House — the fourth floor below
Dinosaur show — the fifth (lowest) floor
On the ground floor there is the Welcome Hall — the entrance where every visitor comes in.
Tip: Above the ground there are six floors — Food Court, Art Centre, Book Store, Ice Cream, Sports Centre and Space. So the building has 6 floors up and 5 floors down.
Q3.
A lift is used to go up and down between the floors. It has two buttons: ‘+’ to go up and ‘–’ to go down. Can you spot the lift?
Answer
Yes — the lift is the tall narrow shaft drawn on the right-hand side of the building. It runs all the way from the topmost floor (Space) down to the lowest floor (Dinosaur), passing through the ground floor.
Its panel has just two buttons:
‘+’ → go up one floor for each press ‘–’ → go down one floor for each press
So pressing + + + (that is + 3) takes you up three floors, and pressing – – – – (that is – 4) takes you down four floors.
Q4.
What do you press to go four floors up? What do you press to go three floors down?
Answer
Four floors up → press ‘+’ four times → + + + + , written as + 4
Three floors down → press ‘–’ three times → – – – , written as – 3
For example, from the Welcome Hall (Floor 0) pressing + 4 takes you to the Ice Cream floor, and pressing – 3 takes you to the Cinema.
Tip: The number after the sign is simply how many times the button is pressed; the sign tells you the direction.