Quadratic Equations | Exercise 4.2

Question 3

Find two numbers whose sum is 27 and product is 182.

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Solution

We will set up a quadratic equation. Then we will solve it to find the numbers.

Step 1 — Formulate the equation

Let's call the first number xx. The sum of the two numbers is 27. So, the second number will be 27x27 - x. Their product is given as 182. We can write this as an equation.

x(27x)=182x(27 - x) = 182

27xx2=18227x - x^2 = 182

x227x+182=0x^2 - 27x + 182 = 0

x227x+182=0\boxed{x^2 - 27x + 182 = 0}

Step 2 — Solve the equation by factoring

We need to find two numbers. Their product is 182. Their sum is -27. These numbers are -13 and -14. Let's split the middle term.

x213x14x+182=0x^2 - 13x - 14x + 182 = 0

x(x13)14(x13)=0x(x - 13) - 14(x - 13) = 0

(x13)(x14)=0(x - 13)(x - 14) = 0

(x13)(x14)=0\boxed{(x - 13)(x - 14) = 0}

Step 3 — Find the numbers

From the factored equation, we have two possibilities. Either x13=0x - 13 = 0 or x14=0x - 14 = 0.

x13=0x - 13 = 0

x=13x = 13

If x=13x = 13, the first number is 13. The second number is 27x27 - x.

2713=1427 - 13 = 14

So the numbers are 13 and 14.

x14=0x - 14 = 0

x=14x = 14

If x=14x = 14, the first number is 14. The second number is 27x27 - x.

2714=1327 - 14 = 13

So the numbers are 14 and 13. Both cases give the same pair of numbers.

Answer

The two numbers are 13 and 14.

More questions in Exercise 4.2

Q1

Find the roots of the following quadratic equations by factorisation:

(i) x23x10=0x^2 - 3x - 10 = 0

(ii) 2x2+x6=02x^2 + x - 6 = 0

(iii) 2x2+7x+52=0\sqrt{2}x^2 + 7x + 5\sqrt{2} = 0

(iv) 2x2x+18=02x^2 - x + \frac{1}{8} = 0

(v) 100x220x+1=0100x^2 - 20x + 1 = 0

Q2

Solve the problems given in Example 1.

Q3

Find two numbers whose sum is 27 and product is 182.

Q4

Find two consecutive positive integers, sum of whose squares is 365.

Q5

The altitude of a right triangle is 7 cm less than its base. If the hypotenuse is 13 cm, find the other two sides.

Q6

A cottage industry produces a certain number of pottery articles in a day. It was observed on a particular day that the cost of production of each article (in rupees) was 3 more than twice the number of articles produced on that day. If the total cost of production on that day was ₹ 90, find the number of articles produced and the cost of each article.

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