Question Details

Directions (46-47): Read the following quadric equation carefully and answer the questions given below.

Equation 1: ax2+bx+c=0
Equation 2: dy2+ey+c=0

Note:
(i) c is a single digit prime number greater than 2
(ii) d and b are two digits prime number less than 20
(iii) d is greater than 11
(iv) b is greater than d
(v) Smallest roots of both the equation are same
(vi) No root is irrational
(vii) e = b + 1
(viii) 3c is greater than b

Find the value of ‘d× e’ .

Options

A

190

B

196

C

225

D

250

E

260

Show Answer

Correct Answer :

Option E

260

260

Solution :

The correct answer is 260.

Step-by-step Explanation:

Let's analyze the given conditions step-by-step to find the values of the variables:

1. Identify the possible values of c, d, and b:
- From note (i), c is a single-digit prime number greater than 2. The prime numbers meeting this condition are:
c{3,5,7}
- From note (ii), d and b are two-digit prime numbers less than 20. The prime numbers meeting this condition are:
{11,13,17,19}
- From note (iii), d is greater than 11. Therefore, d can be:
d{13,17,19}
- From note (iv), b is greater than d (b>d). This implies d cannot be 19. Thus, d can be 13 or 17, and b can be 17 or 19.

2. Apply the condition 3c>b:
- From note (viii), we have 3c>b.
- Since the maximum possible value of c is 7, we have 3c3×7=21.
- For 3c>b to hold, let's test the possible values:
If b=19, then 3c>19. The only prime value for c that satisfies this is c=7 (since 3×7=21>19).
- If b=19, then since d<b and d{13,17}, d can be 13 or 17.

3. Use the quadratic equations and their roots to narrow down:
- Note (vii) states that e=b+1.
- If b=19, then:
e=19+1=20
- Let's test the value of d=13:
Equation 2 becomes: dy2+ey+c=0
13y2+20y+7=0
- Solving this quadratic equation:
13y2+13y+7y+7=0
13y(y+1)+7(y+1)=0
(13y+7)(y+1)=0
The roots are y=-1 and y=-713.
Since -1<-713, the smallest root of Equation 2 is -1.

- According to note (v), the smallest roots of both equations are the same, so x=-1 must be the smallest root of Equation 1:
ax2+bx+c=0
Substitute x=-1, b=19, and c=7:
a(-1)2+19(-1)+7=0
a-19+7=0
a=12
- Let's check Equation 1 with a=12:
12x2+19x+7=0
12x2+12x+7x+7=0
12x(x+1)+7(x+1)=0
(12x+7)(x+1)=0
The roots are x=-1 and x=-712.
The smallest root is indeed -1, and neither root is irrational, satisfying all constraints.

4. Calculate the value of d×e:
Using d=13 and e=20:
d×e=13×20=260

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