Natural Numbers: 1 Mark each
The smallest natural number is 1 and there is no largest natural number as we have infinite natural numbers.

Concept: 1 Mark
Steps: 1 Mark
Answer: 1 Mark
1L=1000ml
Capacity of bottle = 1.5 $\times$1000 = 1500ml

Capacity of glass = 50ml

Number of glasses that can be filled = 1500 $÷$ 50 = 30 glasses
Now if the capacity of glasses = 60ml.
Then, the number of glasses that can be filled = 1500 $÷$ 60= 25 glasses

Each option: 1 Mark
1 Kilogram = 1,000 grams.

a. 40 Kilograms = 40 $\times$ 1000 = 40,000 grams.
b. 120 kilograms = 120 $\times$ 1000 = 1,20,000 grams.

Steps: 2 Marks
Actual Amount: 1 Mark
Estimated Amount: 1 Mark
We need to estimate 1398 - 526.
1398 > 526.
$\therefore$ we will round off these numbers to the nearest hundreds. 
1398 can be rounded off to 1400.
526 can be rounded off to 500.
Estimated difference:
1400 - 500 = 900
The actual amount left with him= 1398 - 526 = 872
The difference between the estimated amount left to him, and the actual amount left with him=900 - 872 = 28.

Steps: 2 Marks
Answer: 1 Mark
The population of a town in 1991 = 78787

and the population of that town in 2001 = 95833

78787 is rounded off the nearest hundreds

= 78800

95833 is rounded off to nearest hundreds

= 95800

$\therefore$ Estimated increase in population

= 95800 – 78800 = 17000

Concept: 1 Mark
Steps: 2 Marks
Answer: 1 Mark
The given digits are 1,3,5,7,6.
Now to find the greatest number, we will arrange the given digits in descending order, i.e. the greatest number to the extreme left, then the next one and so on.
To find the smallest number, we will arrange the digits in an ascending order, i.e. the smallest number to the extreme left and so on.
Greatest number = 76531

Smallest number = 13567

Difference = 76531 - 13567 = 62964
Similarly,
The greatest 4 digit number that can be formed using the given digits = 7653
The least 4 digit number that can be used using the given digits = 1356
The difference between the greatest and the least=7653 - 1356 = 6297

Concept: 1 Mark
Steps: 2 Marks
Answer: 1 Mark
We know that ,1 km = 1000 m
Now total distance walked by Anshul = 5.5 (house to office) +2 km (way back from office)
Now 1 km = 1000m
$\therefore$ 5.5 km = 5.5 $\times$ 1000 = 5500 m
2 km = 2$\times$1000 = 2000 m
Now total distance walked by Anshul = 5.5 + 2 km = 5500 + 2000 = 7500 m

Each part: 1 Mark
a) XXX. 
Now, we now that if a symbol is repeated, its value is added as many times as it occurs.
XXX = 10 + 10 + 10 = 30.
b) IX
I=1
X=10
1<10
If a smaller value is written to the left of a symbol of greater value, its value is subtracted from the value of the greater symbol.
$\therefore$ The value IX = 10 - 1 = 9.
c) VII
If a symbol of smaller value is written to the right of a symbol of greater value, its value gets added to the value of the greater symbol.
V=5
I=1
$\therefore$ The value of VII = 5 + 1 + 1 = 7.
d) XII
In this case, also, the smaller value is written to the right of the greater number. So its value is added to the value of the greater symbol.
XII= 10 + 1 + 1 = 12.