4 Find three integers of which the sum is -9. (Hint: Use two positive integers and one negative integer)

Let's choose 1 and 2.

Let the three integers be $a, b, c$. We have $a=1$ and $b=2$.

So, the three integers are 1, 2, and -12.

The final answer for 3.4 is $\boxed{1, 2, -12}$ (other combinations are possible).

Question 3.5

Let $M$ be the total amount of money Mr. Jacobs had in his wallet initially.

He spent $\frac{1}{2}$ on sweets and $\frac{1}{3}$ on soft drinks.
Total fraction spent $= \frac{1}{2} + \frac{1}{3}$.
To add these fractions, find a common denominator, which is 6.

The fraction of money remaining is $1 - \text{total fraction spent}$.

We are told that R25 is remaining, which represents $\frac{1}{6}$ of the initial money.

Multiply both sides by 6:

The final answer for 3.5 is $\boxed{\text{R}150}$.

Question 4.1.1

The pattern grows by adding a new row of squares at the top in each subsequent stage. The number of squares in the new row is equal to the stage number. The total number of squares in each stage is the sum of consecutive integers from 1 up to the stage number.

Question 4.1.2

Stage 1: 1 square
Stage 2: $1 + 2 = 3$ squares
Stage 3: $1 + 2 + 3 = 6$ squares
This is a sequence of triangular numbers, where the number of squares in stage $n$ is given by the formula $T_n = \frac{n(n+1)}{2}$.

Substitute $n = 40$ into the formula:

The final answer for 4.1.2 is $\boxed{820 \text{ squares}}$.