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CBSE Class 9 Mathematics Question 1 of 17

Proofs in Mathematics — Question 1

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Question 1

State whether the following statements are always true, always false or ambiguous. Justify your answers.

(i) There are 13 months in a year.

(ii) Diwali falls on a Friday.

(iii) The temperature in Magadi is 26°C.

(iv) The earth has one moon.

(v) Dogs can fly.

(vi) February has only 28 days.

Answer

(i) This statement is always false, as there are 12 months in a year.

(ii) This statement is ambigious, because it is not necessary that Diwali falls on a Friday every year.

(iii) This statement is ambiguous, because temperature does not remains fixed. At some time in the year, the temperature in Magadi, could be less than or greater than 26°C.

(iv) This statement is always true, because the earth has only one moon.

(v) This statement is always false, because dogs cannot fly.

(vi) This statement is ambiguous, because in a leap year, February has 29 days and in non-leap years February has 28 days.