Convert "sawa sau lah" to a decimal fraction, and express "8.5 rupees" and "50 meters 4 cm" in their respective units.

$8.5 \text{ rupees} = 8 \text{ rupees} + 0.5 \text{ rupees}$

Since $1 \text{ rupee} = 100 \text{ paisa}$,
$0.5 \text{ rupees} = 0.5 \times 100 \text{ paisa} = 50 \text{ paisa}$
So, $8.5 \text{ rupees}$ means $\boxed{\text{8 روپے 50 پیسے}}$.

c) 50 میٹر 4 سم یعنی (50 meters 4 cm means)

Since $1 \text{ meter} = 100 \text{ cm}$,
$4 \text{ cm} = \frac{4}{100} \text{ meters} = 0.04 \text{ meters}$

$50 \text{ meters} + 0.04 \text{ meters} = 50.04 \text{ meters}$
So, $50 \text{ meters } 4 \text{ cm}$ means $\boxed{\text{50.04 میٹر}}$.

d) سوا سو لہ اس کسر کو عشری علامت کا استعمال کر کے لکھیے۔ (Write "sawa sau lah" as a decimal fraction.)
The term "سوا" (sawa) means "one and a quarter" or $1 \frac{1}{4}$. The instruction asks to write this as a decimal fraction.

$1 \frac{1}{4} = \frac{1 \times 4 + 1}{4} = \frac{5}{4}$

$\frac{5}{4} = 1.25$
(The terms "سو لہ" appear to be extraneous or a typo in this context, as "سوا" directly translates to the required decimal fraction.)
The decimal fraction is $\boxed{\text{1.25}}$.

Question 8:

a) ذیل کے اعداد میں مثلثی عدد کے گرد دائرہ بنائیے۔ (Circle the triangular number among the following numbers.)
The given numbers are: 4, 5, 6, 8, 9, 10, 12.
Triangular numbers are numbers obtained by summing consecutive positive integers starting from 1.
The sequence of triangular numbers is:
$T_1 = 1$
$T_2 = 1+2 = 3$
$T_3 = 1+2+3 = 6$
$T_4 = 1+2+3+4 = 10$
$T_5 = 1+2+3+4+5 = 15$
From the given list, the triangular numbers are 6 and 10. Since the question asks for "the" triangular number (singular), we will identify the first one in the list.
The triangular number is $\boxed{\text{6}}$.

b) ذیل کے تواتر کو مکمل کیجیے۔ (Complete the following sequence.)
The sequence is: 10, 15, 21, .........

$15 - 10 = 5$
$21 - 15 = 6$

The differences are increasing by 1 (5, then 6). So, the next difference should be 7.

Next term = $21 + 7 = 28$
The completed sequence is 10, 15, 21, $\boxed{\text{28}}$.

c) ذیل کے تواتر کو مکمل کیجیے۔ (Complete the following sequence.)
The sequence shows patterns of dots:

• First image: 5 rows of 5 dots, total $5 \times 5 = 25$ dots.
• Second image: 4 rows of 4 dots, total $4 \times 4 = 16$ dots.
• Third image: 3 rows of 3 dots, total $3 \times 3 = 9$ dots. The pattern is a sequence of decreasing perfect squares: $5^2, 4^2, 3^2$.

The next term should be $2^2 = 4$ dots.
The term after that should be