95
92
To find the number of ducks in the zoo, we use the given information: There are 160 heads and 450 legs. Let the number of ducks be \(d\) and the number of rabbits be \(r\). Since each duck and rabbit has one head, we have the equation:
\(d + r = 160\)
Each duck has 2 legs and each rabbit has 4 legs. Thus, the second equation is:
\(2d + 4r = 450\)
We can simplify the second equation by dividing it by 2:
\(d + 2r = 225\)
Now, we have the system of equations:
\(1. \quad d + r = 160\)
\(2. \quad d + 2r = 225\)
Subtract equation 1 from equation 2:
\((d + 2r) - (d + r) = 225 - 160\)
\(r = 65\)
Substitute \(r = 65\) back into equation 1:
\(d + 65 = 160\)
\(d = 160 - 65\)
\(d = 95\)
Therefore, the number of ducks in the zoo is 95.
Directions: In Question Numbers 19 and 20, a statement of Assertion (A) is followed by a statement of Reason (R).
Choose the correct option from the following:
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Assertion (A) is false, but Reason (R) is true.
Assertion (A): For any two prime numbers $p$ and $q$, their HCF is 1 and LCM is $p + q$.
Reason (R): For any two natural numbers, HCF × LCM = product of numbers.