Introduction to Linear Polynomials | Exercise 2.2

Question 5

Ruby has 3 times as many two-rupee coins as she has five rupee-coins. If she has a total ₹88, how many coins does she have of each type?

Check your answer with HomiSolve it yourself, then let Homi check your steps and spot mistakes.
Solution

We will form a linear equation based on the given information and solve it.

Step 1 — Formulating the equation

Let's assume the number of five-rupee coins. Let the number of five-rupee coins be x\mathbf{x}. Ruby has 3 times as many two-rupee coins. So, the number of two-rupee coins is 3x\mathbf{3x}. The value from five-rupee coins is 5×x5 \times x. The value from two-rupee coins is 2×3x2 \times 3x. The total value of all coins is ₹88. We can write an equation for the total value.

5x+2(3x)=885x + 2(3x) = 88

5x+6x=885x + 6x = 88

11x=8811x = 88

x=8811x = \frac{88}{11}

x=8\boxed{x = 8}

Diagram 1

Step 2 — Finding the number of coins

We found the value of x\mathbf{x} in the previous step. The number of five-rupee coins is x\mathbf{x}.

Number of five-rupee coins=8\text{Number of five-rupee coins} = 8

The number of two-rupee coins is 3x\mathbf{3x}.

Number of two-rupee coins=3×8\text{Number of two-rupee coins} = 3 \times 8

Number of two-rupee coins=24\text{Number of two-rupee coins} = 24

Answer

(i) Number of five-rupee coins = 8 (ii) Number of two-rupee coins = 24

More questions in Exercise 2.2

Q1

Find the value of the linear polynomial 5x35x - 3 if:

(i) x=0x = 0 (ii) x=1x = -1 (iii) x=2x = 2

Q2

Find the value of the quadratic polynomial 7s24s+67s^2 - 4s + 6 if:

(i) s=0s = 0 (ii) s=3s = -3 (iii) s=4s = 4

Q3

The present age of Salil's mother is three times Salil's present age. After 5 years, their ages will add up to 70 years. Find their present ages.

Q4

The difference between two positive integers is 63. The ratio of the two integers is 2:5. Find the two integers.

Q5

Ruby has 3 times as many two-rupee coins as she has five rupee-coins. If she has a total ₹88, how many coins does she have of each type?

Q6

A farmer cuts a 300 feet fence into two pieces of different sizes. The longer piece is four times as long as the shorter piece. How long are the two pieces?

Q7

If the length of a rectangle is three more than twice its width and its perimeter is 24 cm, what are the dimensions of the rectangle?

← Back to Introduction to Linear Polynomials