Laying the integers out in order, and why −8 is less than −2

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What to assume they know

Numbering the floors below the ground: why zero needs another side: signed floor numbers, Floor 0, and the ray that stops
Addition as movement: starting position plus movement gives target position: movement as a signed number on a vertical shaft
Comparing whole numbers with < and >, and reading those symbols aloud
Reading an evenly spaced scale and interpolating between two marked ticks

What they should be able to do

Compare two floor numbers by saying which floor is lower
Use < and > correctly between two signed numbers, including two negatives
State why every negative number is below 0 and every positive number above it
Read an unlabelled tick on a marked vertical scale by counting from a labelled one
Explain why there is no lowest integer, in the same words as why there is no greatest
Name the set the chapter calls the integers, and say what it contains
Rotate the vertical scale into the number line and say what "left" now means
Explain the convention of dropping the '+' sign, and what is lost and kept by it
Use an unmarked number line to place numbers whose scale would not fit on paper

Where it usually goes wrong

"– 8 is bigger than – 2 because 8 is bigger than 2." The single most common error in the chapter. Correct it by putting both on the shaft and asking which one you would have to go down to reach.
"The minus sign makes the number small, so all negatives are about the same." They are spread out exactly as widely as the positives, and in the same order, reversed. Show both halves of the line at once.
"Zero is the smallest number." It was, while the picture was a ray. It is now the middle of the picture, and the chapter's opening question was precisely whether the ray was the whole story.
"There must be a most negative number, the way there is a ground floor." The ground floor exists because someone built it. The numbers do not stop for the same reason the counting numbers do not stop going up.
"Writing 3 instead of + 3 changes what the number is." It changes only what is written. The convention is stated on p.252 and is worth naming as a convention, so that a bare 3 in a later exercise is not read as a different object from + 3.
"An unmarked number line is a number line someone forgot to finish." It is a deliberate tool: it lets you place 250 and – 100 on the same picture, which no unit-spaced line on a page can do.

Questions to check understanding

Insert < or > between two signed numbers, including two negatives
Arrange a given list of integers in increasing or decreasing order
Read the value at an unlabelled tick, given two labelled ones
Mark a stated integer on a number line
List every integer strictly between two given integers
State, with a reason, whether there is a least integer
Say which of two people described by their locations is lower
The solutions block bound with this chapter file answers the p.246, p.247 and p.253 exercises on its footer pages 2–3 and 5

Examples worth working on the board

Four people in four shops (p.246). Jay stands in the Art Centre, Asin in the Sports Centre, Binnu in the Cinema Centre, Aman in the Toy Store. Only Jay's floor is stated; the other three are to be read off the building. The question asked is who is lowest.
The two model comparisons (p.247). + 3 against + 4, and – 3 against – 4. The book settles the first, then poses the second as a question, then settles it the same way. That staging is the argument and should be kept.
Six comparisons set on the drawn building (p.247). – 2 and + 5; – 5 and + 4; – 5 and – 3; + 6 and – 6; 0 and – 4; 0 and + 4. Five of the six lie inside the range the building actually has, which p.250 gives as – 5 to + 6. The fourth does not: – 6 is one floor below the lowest floor drawn. The book still sets it under the Building of Fun. Either is fine; pretending – 6 is on the picture is not.
Six more that do not fit (p.247). – 10 and – 12; + 17 and – 10; 0 and – 20; + 9 and – 9; – 25 and – 7; + 15 and – 17. The instruction is to imagine the building taller. That instruction is section 8's setup.
The lettered vertical building (p.247). Checked against the printed page and by counting ticks. A vertical line with arrowheads at both ends carries evenly spaced ticks; eight of them are lettered A to H. Four numbers are printed beside the line — + 1 at E, 0 on the unlettered tick between E and D, – 1 at D, and – 12 at A. The running text of the question names only three of these, leaving out the 0, but the 0 is on the artwork and it is what anchors the scale, so a redraw has to carry it. The five lettered ticks left without numbers are to be found by counting — B, C, F, G, H sit at – 9, – 6, + 2, + 6 and + 11. A second task asks for four further floors to be marked: – 7, – 4, + 3 and – 10.
The boxed question on how many negatives there are (p.250). It contrasts the building's range, – 5 to + 6, with the mine's, and then names the integers. This box is where the chapter stops being about one building.
The number line (p.252). Marked – 10 to 10 at unit spacing, arrowheads at both ends. The book gets it by rotating the infinite lift a quarter turn. Checked against the printed page.
Three orderings printed on that page (p.252). 2 against 5; – 3 against 2; – 5 against – 3. The third is the one the whole topic exists for.
Marking your own (p.253). Three positive and three negative numbers to be chosen freely and then written in increasing order. Leave the choice free — the exercise's point is that any choice works.
The unmarked number line (p.254). A line with arrowheads at both ends and a single tick labelled 0. Checked against the printed page.

Figures to have open

The lettered vertical line with evenly spaced ticks, carrying the four printed numbers + 1, 0, – 1 and – 12, with five lettered ticks left blank. This must be redrawn faithfully enough that counting ticks gives the right answers — the tick spacing carries the mathematics, and the 0 is what fixes it to the scale.
A number line marked – 10 to 10 with arrowheads at both ends. Reused throughout the chapter.
An unmarked number line: two arrowheads and a single labelled 0.
The rotation in section 9 is a movement, not a still, and is the one figure of this topic that has to move.
No photograph or textbook data table is needed.

Where this sits in the book

NCERT Ganita Prakash, Class 6, Chapter 10 "The Other Side of Zero", §10.1 "Bela's Building of Fun", p.246 — the named sub-heading on comparing by floor, and the four people
§10.1, p.247 — the two model comparisons, the boxed remark on where the negatives sit, the twelve comparisons, and the lettered vertical building
§10.1, p.250 — the boxed question on how many negative numbers there are, and the naming of the integers
§10.1, p.252 — the named sub-heading returning to the number line, the rotation, the dropped plus sign, and the three printed orderings
§10.1, p.253 — marking and ordering your own numbers
§10.1, p.254 — the named sub-heading on the unmarked number line
Chapter Summary, p.269, for positive integers, negative integers, and the printed chain of inequalities
Solutions block bound with this chapter file, footer pages 2–3 and 5