A good Mathematics textbook contains a lot of
questions for practice
questions for exploration
worked out,examples
theorems and proofs
Consider the following statement. "Every odd natural number is a prime number." Which of the following methods of "proof can be used to prove/disprove the above statement?
Direct proof
Method of disproof
Proof by contrapositive
Proof by contradiction
B.
Method of disproof
"Every odd natural number is a prime number". Method of disproof is used to disprove the above statement.
As in method of disproof, we can disprove the statement with the help of counter example. e.g. Let us assume a odd number = 9
9 is an odd positive natural number but it is not a prime number.
In the product of (9x + 15 - x) and ( - 1 - x + x2), if A, B and C are the coefficients of x3, x2 and x respectively, then the value of (A + B - C) is
- 3
14
- 17
11
A person marks his goods 40% above the cost price and allows 40% discount on the marked price. His loss/gain percent is
loss, 8%
No loss/gain
gain, 10%
loss, 16%
Two sides of a right triangle measure 15 cm and 17 cm. Which of the following statements can be true of the length of the third side of the triangle ?
A. It is between 4 cm and 7 cm.
B. It is between 20 cm and 23 cm.
C. It is less than 10 cm
Only B
A and C
A and B
B and C
A tank is in the form of a cuboid. It holds a maximum of 540 m3 water. If the tank is 8 m long and 15 m wide, then how many metres,deep must the water be when the tank is full ?
2
4.5
2.5
3