Rational numbers: Class 7 maths video

0:00 Class 7 maths. Rational numbers.

0:03 Welcome aboard Captain Calc's math mission on rational numbers!

0:08 Today we will explore numbers in p/q form, compare them, and master fractions with positive and negative signs.

0:16 Understanding Rational Numbers.

0:19 A rational number is any number that can be written in the form p/q, where p and q are integers and q is not zero.

0:28 If p and q have the same sign, the rational number is positive.

0:33 Try this one. Is -7 a rational number?

0:38 Write -7 as a fraction with denominator 1: -7/1.

0:44 Here p = -7 and q = 1, both are integers and q is not zero.

0:51 So the answer is Yes.

0:53 Equivalent Forms and Standard Form.

0:56 Multiplying or dividing both numerator and denominator by the same non-zero integer gives an equivalent rational number.

1:06 A rational number is in standard form when its denominator is positive and the highest common factor of numerator and denominator is 1.

1:16 Try this one. Find an equivalent rational number for -2/3 with denominator 12.

1:25 Multiply denominator 3 by 4 to get 12.

1:29 Multiply numerator -2 by 4 to get -8.

1:33 So the answer is -8/12.

1:37 Comparing Rational Numbers.

1:39 To compare rational numbers, make their denominators positive and equal using the LCM.

1:46 Once denominators are equal, compare the numerators.

1:50 Try this one. Which is greater: -3/4 or -5/4?

1:57 Both denominators are 4.

2:00 Compare numerators: -3 is greater than -5.

2:05 So -3/4 is greater than -5/4.

2:10 So the answer is -3/4.

2:13 Operations on Rational Numbers.

2:16 To add or subtract, convert to a common denominator, then add or subtract numerators.

2:23 To multiply, multiply numerators together and denominators together.

2:28 Try this one. Solve: -3/5 + 2/5

2:35 Denominators are equal.

2:37 Add numerators: (-3 + 2) / 5 = -1/5.

2:44 So the answer is -1/5.

2:47 Your turn. Is -3/-8 positive or negative? Pause the video, and try it.

2:56 The answer is positive.

2:58 Well done! Now try the practice and the quiz in this lesson on LearnFun.