Belongs to the unit Real Numbers

1. Find 5 irrational numbers between 4 and 5.

**Solution:**

The numbers a = 4.101001000….

b = 4.02002000…..

c = 4.303003000……

d = 4.404004000……

e = 4.05005000…..

Are 5 irrational numbers between 4 and 5 since 4 < a < b < c < d < e < 5

2. Find 6 rational numbers between √𝟐 and √𝟑

**Solution:**

Let √2,

Therefore, √𝟐 = 1.414213

Let √3,

√3 = 1.7320508

We consider r_{1} = 1.422222……..

r_{2} = 1.433333…….

r_{3} = 1.44444……..

r_{4} = 1.5555……..

r_{5} = 1.666666……

r_{6} = 1.7111111……

These are rational numbers between 2 and 3

√2< r_{1}< r_{2} < r_{3} < r_{4} < r_{5} < r_{6} < √3

3. Write 5 irrational numbers between √𝟑 and √𝟓

**Solution:**

Therefore, √3 = 1.7320508

Then, √5,

Therefore, √5 = 2.236067

Consider a = 1.7404004000……

b = 1.7505005000……

c = 1.8202002000……

d = 1.9303003000……

e = 2.101001000… are 5 irrational numbers between √3 and √5

4. Prove that √2 + √5 is irrational.

**Solution:**

If possible, let √2 + √5 be rational

Then (√2 + √5) is rational

═> (√2 + √5) is rational

═> 2 + 5 + 2√2 .√5

═> 7 + 2 √10 is rational

But (7 + 2 √10 ) being the sum of a rational and an irrational. These we arrive at a contradiction to the assumption that ( √2 + √5 ) is rational.

Hence is ( √2 + √5 ) is irrational

5. Give an example of an irrational number such that its 8-th power is a rational number.

**Solution:**

√2^{8} = 2^{1/8} is an irrational number.

The 8th power is (2^{1/8} )^{8} = 2^{1/8 x 8} = 2^{1} = 2

2 is a rational number.

6. Why is 0.111222333444……., where each number appears 3 times in a row. Irrational?

**Solution: **

0.111222333444….., where each number appears 3 times in a row is a non- terminating, non-recurring decimal expansion. Hence it is irrational.

7. Find 3 rational numbers between 0.1122334455….. and 0.1234567…. here each number appears 2 times in the first expansion and each number appears only once in the second expansion.

**Solution:**

Consider r_{1} = 0.12222…..

r_{2} = 0.122333…..

r_{3} = 0.122444……

r_{4} = 0.122555……

r_{5} = 0.122666……

This is 5 rational numbers between 0.1122334455….. and 0.1234567……

8. Find the 3 irrational numbers between 2/3 and ¾ using their decimal expansion.

**Solution:**

Consider a = 0.6707007000….

b = 0.6808008000….

c = 0.6909009000…

d = 0.707007000….

e = 0.7202002000….

These are 5 irrational numbers and 2/3 < a < b < c < d < e < 3/4