Tamilnadu State Board New Syllabus Samacheer Kalvi 8th Maths Guide Pdf Chapter 1 Numbers Ex 1.2 Textbook Questions and Answers, Notes.
Tamilnadu Samacheer Kalvi 8th Maths Solutions Chapter 1 Numbers Ex 1.2
Question 1.
Fill in the blanks:
(i) The value of \(\frac{-5}{12}+\frac{7}{15}\) = ________ .
Answer:
\(\frac{1}{20}\)
(ii) The value of \(\left(\frac{-3}{6}\right) \times\left(\frac{18}{-9}\right)\) is = ________ .
Answer:
1
(iii) The value of \(\left(\frac{-15}{23}\right) \div\left(\frac{30}{-46}\right)\) is ________ .
Answer:
1
(iv) The rational number ________ does not have a reciprocal.
Answer:
0
(v) The multiplicative inverse of -1 is ________ .
Answer:
-1
Question 2.
Say True or False
(i) All rational numbers have an additive inverse.
Answer:
True
(ii) The rational numbers that are equal to their additive inverses are 0 and -1.
Answer:
False
(iii) The additive inverse of \(\frac{-11}{-17}\) is \(\frac{11}{17}\)
Answer:
False
(iv) The rational number which is its own reciprocal is -1.
Answer:
True
(v) The multiplicative inverse exists for all rational numbers.
Answer:
False
Question 3.
Find the sum
(i) \(\frac{7}{5}+\frac{3}{5}\)
(ii) \(\frac{7}{5}+\frac{5}{7}\)
(iii) \(\frac{6}{5}+\left(\frac{-14}{15}\right)\)
(iv) \(-4 \frac{2}{3}+7 \frac{5}{12}\)
Answer:
(i) \(\frac{7}{5}+\frac{3}{5}\)
(ii) \(\frac{7}{5}+\frac{5}{7}\)
(iii) \(\frac{6}{5}+\left(\frac{-14}{15}\right)\)
(iv) \(-4 \frac{2}{3}+7 \frac{5}{12}\)
Question 4.
Subtract \(\frac{-8}{44}\) from \(\frac{-17}{11}\)
Answer:
Question 5.
Evaluate
(i) \(\frac{9}{132} \times \frac{-11}{3}\)
(ii) \(\frac{-7}{27} \times \frac{24}{-35}\)
Answer:
(i) \(\frac{9}{132} \times \frac{-11}{3}\)
(ii) \(\frac{-7}{27} \times \frac{24}{-35}\)
Question 6.
Divide
(i) \(\frac{-21}{5}\) by \(\frac{-7}{-10}\)
(ii) \(\frac{-3}{13}\) by -3
(iii) -2 by \(\frac{-6}{15}\)
Answer:
(i) \(\frac{-21}{5}\) by \(\frac{-7}{-10}\)
(ii) \(\frac{-3}{13}\) by -3
(iii) -2 by \(\frac{-6}{15}\)
Question 7.
Find (a + b) ÷ (a – b) if
(i) a = \(\frac{1}{2}\), b = \(\frac{2}{3}\)
(ii) a = \(\frac{-3}{5}\), b = \(\frac{2}{15}\)
Answer:
(i) a = \(\frac{1}{2}\), b = \(\frac{2}{3}\)
(ii) a = \(\frac{-3}{5}\), b = \(\frac{2}{15}\)
Question 8.
Simplify \(\frac{1}{2}+\left(\frac{3}{2}-\frac{2}{5}\right) \div \frac{3}{10} \times 3\) and show that it is a rational number between 11 and 12.
Answer:
Question 9.
Simplify
(i) \(\left[\frac{11}{8} \times\left(\frac{-6}{33}\right)\right]+\left[\frac{1}{3}+\left(\frac{3}{5} \div \frac{9}{20}\right)\right]-\left[\frac{4}{7} \times \frac{-7}{5}\right]\)
(ii) \(\left[\frac{4}{3} \div\left(\frac{8}{-7}\right)\right]-\left[\frac{3}{4} \times \frac{4}{3}\right]+\left[\frac{4}{3} \times\left(\frac{-1}{4}\right)\right]\)
Answer:
(i) \(\left[\frac{11}{8} \times\left(\frac{-6}{33}\right)\right]+\left[\frac{1}{3}+\left(\frac{3}{5} \div \frac{9}{20}\right)\right]-\left[\frac{4}{7} \times \frac{-7}{5}\right]\)
(ii) \(\left[\frac{4}{3} \div\left(\frac{8}{-7}\right)\right]-\left[\frac{3}{4} \times \frac{4}{3}\right]+\left[\frac{4}{3} \times\left(\frac{-1}{4}\right)\right]\)
Question 10.
A student had multiplied a number by \(\frac{4}{3}\) instead of dividing it by \(\frac{4}{3}\) and got 70 more than the correct answer. Find the number.
Answer:
Let the number = a
Objective Type Questions
Question 11.
The standard form of the sum \(\) is ________ .
(A) 1
(B) \(\frac{-1}{2}\)
(C) \(\frac{1}{12}\)
(D) \(\frac{1}{22}\)
Answer:
1
Hint:
Question 12.
\(\left(\frac{3}{4}-\frac{5}{8}\right)+\frac{1}{2}\) = _______ .
(A) \(\frac{15}{64}\)
(B) 1
(C) \(\frac{5}{8}\)
(D) \(\frac{1}{16}\)
Answer:
(C) \(\frac{5}{8}\)
Hint:
Question 13.
\(\frac{3}{4}+\left(\frac{5}{8}+\frac{1}{2}\right)\) =
(A) \(\frac{13}{10}\)
(B) \(\frac{2}{3}\)
(C) \(\frac{3}{2}\)
(D) \(\frac{5}{8}\)
Answer:
(B) \(\frac{2}{3}\)
Hint:
Question 14.
\(\) = _______ .
(A) \(\frac{5}{8}\)
(B) \(\frac{2}{3}\)
(C) \(\frac{15}{32}\)
(D) \(\frac{15}{16}\)
Answer:
(D) \(\frac{15}{16}\)
Hint:
Question 15.
Which of these rational number which have additive inverse?
(A) 7
(B) \(\frac{-5}{7}\)
(C) 0
(D) all of these
Answer:
(D) all of these
Hint:
Additive inverse of 7 is -7
Additive inverse of \(\frac{-5}{7}\) is \(\frac{5}{7}\)
Additive inverse of 0 is 0