# IGCSE Mathematics Paper-1: Specimen Questions with Answers 47 - 50 of 324

## Question 47

### Write in Short

Make the subject of the formula:

Here, formula is

So,

## Question 48

### Write in Short

In the diagram, PQ, ₹ and MN are parallel lines. Angle and angle . Calculate angle QRM.

### Explanation

Here, PQ, ₹ are straight lines.

• So, angles PQR and QRS will be alternate interior angles which will be always same.
• So, angle .
• Now, ₹ and MN are also straight lines, so R and M will be supplementary angles which adding gives

So,

Now, .

## Question 49

### Write in Short

Rosely changed a traveler՚s cheque for 500 pounds £ into dollars when she visited the USA. The exchange rate was 1 pound = 1.54 dollars. How many dollars did she receive?

### Explanation

Here,

1 pound = 1.54 dollars.

Now, Rosely wants To change 500 pounds into dollars.

So, 1 pound = 1.54 dollars

500 pounds = ? dollars

.

## Question 50

### Describe in Detail

Essay▾

Solve

(a) (i) Write the above expression with each number rounded to one significant figure.

(ii) Use your answer to find an estimate for the value of the expression.

(b) Solve the value of the original expression. Give your answer correct to 1 decimal place.

### Explanation

Here,

(a) Here, expression is .

Now, by rounding each number to one significant figure:

• So, 9.12 will be 9 because after decimal point there is 1 which is less than 5, so 9 will remain same.
• 2.35 will be 2 because after decimal point there is 3 which is less than 5, so 2 will remain same.
• 3.06 will be 3 because after decimal point there is 0 which is less than 5, so 3 will remain same.
• 2.57 will be 3 because after decimal point there is 5 which is greater than 5, so 2 will be rounded and be 3.

So, expression will be like: .

(b) Here, answered expression after changing to one significant figure is:

• So, it will be like:
• So, as per BODMAS (Brackets, Order (Exponent) , Division, multiplication, Addition, Subtraction) first of all we have to remove brackets and in brackets there are to calculations from which multiplication will take place first:
• Now, in brackets subtraction will be:
• At last, division will be:

(c) Here, original expression is: .

• So, it will be like:
• So, as per BODMAS (Brackets, Order (Exponent) , Division, multiplication, Addition, Subtraction) first of all we have to remove brackets and in brackets there are to calculations from which multiplication will take place first:
• Now, in brackets subtraction will be:
• At last, division will be:

Now, correct it to one decimal place we will get: because there is 5 after digit 7, which is greater than 5, so 7 will be rounded and be 8.