21.

When doing exponents, the work observed in a learner's notebook was as follows

4³ x 4² = 4⁵ , 6⁴ x 6⁴ = 6⁸ , 7³ x 3⁷ = 21¹⁰

The learner has not understood how to

• add exponents and multiply
  
  

• multiply numbers with same base
  
  

• multiply numbers with different bases
  
  

• add exponents

The least number which is a perfect square and is also divisible by 10, 12, 15 and 18 is

• 1600

• 900

• 3600

• 2500

4-(2-9)⁰+3²$÷$1+3

• 15

• 12

• 17

• 16

Given the numbers 3.75 X 10^-7, $3\frac{3}{4}$ X 10^-7, 375 X 10^-9, and $\frac{3}{8}$ X 10^-7. Which of these is not equal to 0.000000375?

• 375 X 10^-7

• $\frac{3}{8}$ X 10^-7

• 3.75 X 10^-7

• $3\frac{3}{4}$ X 10^-7

When the number 3⁹⁸ is divided by 5, the remainder is

• 3

• 1

• 4

• 2

Which of the fractions is the least?

• $\frac{99}{100}$

• $\frac{68}{69}$

• $\frac{24}{25}$

• $\frac{10}{11}$

The remainder obtained when 2³¹ is divided by 5

• 1

• 2

• 3

• 4

If means x, x means +, + means + and + means -, then find the value of 14 - 10 x 4 + 16 + 8

• 6

• 142

• 134

• 2

Simplify $3÷\left[\left(8-5\right)÷\left\{\left(4-2\right)÷\left(2+\frac{8}{13}\right)\right\}\right]$

• $\frac{13}{17}$

• $\frac{17}{13}$

• $\frac{68}{13}$

• $\frac{13}{68}$

Find the value of  $\sqrt{42-\sqrt{42-\sqrt{42}}}......\infty$

• 3

• 6

• 7

• 14