Make up as many expressions with numbers (no variables) as you can from three numbers 5, 7 and 8. Every number should be used not more than once. Use only addition, subtraction and multiplication.

(Hint: Three possible expressions are 5 + (8 − 7), 5 − (8 − 7), (5 × 8) + 7;

make the other expressions.)

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Solution

Many expressions can be formed by using the three numbers 5, 7, and 8.

Some of these are as follows.

5 × (8 − 7)

5 × (8 + 7)

(8 + 5) ×7

(8 − 5) ×7

(7 + 5) ×8

(7 − 5) ×8

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Similar questions

Make up as many expressions with numbers (no variables) as you can from three numbers 5, 7 and 8. Every number should be used not more than once. Use only addition, subtraction and multiplication.

(Hint: Three possible expressions are 5 + (8 − 7), 5 − (8 − 7), (5 × 8) + 7;

make the other expressions.)

Make up as many expressions with numbers (no variables) as you from three numbers 5, 7 and 8. Every number should be used not more than once. Use only addition, subtraction and multiplication.

Question 1

Make up as many expressions with numbers (no variables) as you can from three numbers 5, 7 and 8. Every number should be used not more than once. Use only addition, subtraction and multiplication.

Using commutativity and associativity of addition of rational numbers, express each of the following as a rational number:

(i) $\frac{2}{5} + \frac{7}{3} + \frac{- 4}{5} + \frac{- 1}{3}$

(ii) $\frac{3}{7} + \frac{- 4}{9} + \frac{- 11}{7} + \frac{7}{9}$

(iii) $\frac{2}{5} + \frac{8}{3} + \frac{- 11}{15} + \frac{4}{5} + \frac{- 2}{3}$

(iv) $\frac{4}{7} + 0 + \frac{- 8}{9} + \frac{- 13}{7} + \frac{17}{21}$

Q. How many numbers with not more than three digits can be formed using only the digits

1

through

7

with no digit used more than once in a given number?

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Many expressions can be formed by using the three numbers 5, 7, and 8. Some of these are as follows. 5 × (8 − 7) 5 × (8 + 7) (8 + 5) ×7 (8 − 5) ×7 (7 + 5) ×8 (7 − 5) ×8

Many expressions can be formed by using the three numbers 5, 7, and 8.

Some of these are as follows.

5 × (8 − 7)

5 × (8 + 7)

(8 + 5) ×7

(8 − 5) ×7

(7 + 5) ×8

(7 − 5) ×8