Mental Maths Practise Year 5 Worksheets - Free Printable

Let's solve each problem step by step:

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1) Work out 0.7 + 0.8

- Add the decimals directly:
\[
0.7 + 0.8 = 1.5
\]
- Answer: \( \boxed{1.5} \)

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2) Write the Roman numerals XXXVII in figures.

- Break down the Roman numeral:
- \( X = 10 \)
- \( V = 5 \)
- \( I = 1 \)
- \( XXX = 30 \) (three \( X \)'s)
- \( VII = 7 \) (five plus two ones)
- Combine: \( 30 + 7 = 37 \)
- Answer: \( \boxed{37} \)

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3) Which of these fractions is equivalent to a half?

- The fractions given are:
\[
\frac{1}{3}, \frac{2}{5}, \frac{3}{6}, \frac{4}{9}, \frac{5}{8}
\]
- A fraction is equivalent to \( \frac{1}{2} \) if it simplifies to \( \frac{1}{2} \).
- Check each fraction:
- \( \frac{1}{3} \): Not equivalent.
- \( \frac{2}{5} \): Not equivalent.
- \( \frac{3}{6} \): Simplifies to \( \frac{1}{2} \) (divide numerator and denominator by 3).
- \( \frac{4}{9} \): Not equivalent.
- \( \frac{5}{8} \): Not equivalent.
- Answer: \( \boxed{\frac{3}{6}} \)

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4) 42 ÷ 6

- Perform the division:
\[
42 \div 6 = 7
\]
- Answer: \( \boxed{7} \)

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5) Write down the number eighteen thousand and twenty-seven

- Convert the words to digits:
- Eighteen thousand: \( 18,000 \)
- Twenty-seven: \( 27 \)
- Combine: \( 18,000 + 27 = 18,027 \)
- Answer: \( \boxed{18,027} \)

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6) Fill in the missing number 4081 = 4001 + ___

- Let the missing number be \( x \):
\[
4081 = 4001 + x
\]
- Solve for \( x \):
\[
x = 4081 - 4001 = 80
\]
- Answer: \( \boxed{80} \)

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7) Write down two numbers with a sum of 9 and a difference of 1.

- Let the two numbers be \( a \) and \( b \) where \( a > b \).
- Given:
\[
a + b = 9 \quad \text{(sum)}
\]
\[
a - b = 1 \quad \text{(difference)}
\]
- Add the two equations:
\[
(a + b) + (a - b) = 9 + 1
\]
\[
2a = 10 \implies a = 5
\]
- Substitute \( a = 5 \) into \( a + b = 9 \):
\[
5 + b = 9 \implies b = 4
\]
- Answer: \( \boxed{5 \text{ and } 4} \)

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8) How many vertices in a triangular pyramid?

- A triangular pyramid (tetrahedron) has 4 vertices.
- Answer: \( \boxed{4} \)

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9) Write all down the factors of 15.

- Factors of 15 are numbers that divide 15 evenly:
\[
1, 3, 5, 15
\]
- Answer: \( \boxed{1, 3, 5, 15} \)

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10) Add together \( 6\% \), 5, and \( 3\% \).

- Convert percentages to decimals:
\[
6\% = 0.06, \quad 3\% = 0.03
\]
- Add the numbers:
\[
0.06 + 5 + 0.03 = 5.09
\]
- Answer: \( \boxed{5.09} \)

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11) I have £10. I spend £2.70. How much do I have left?

- Subtract the amount spent from the total:
\[
10 - 2.70 = 7.30
\]
- Answer: \( \boxed{£7.30} \)

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12) What is the value of \( x + 7 \) when \( x = 3 \)?

- Substitute \( x = 3 \) into the expression:
\[
x + 7 = 3 + 7 = 10
\]
- Answer: \( \boxed{10} \)

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13) What is \( \frac{1}{3} \) of 21?

- Multiply 21 by \( \frac{1}{3} \):
\[
\frac{1}{3} \times 21 = \frac{21}{3} = 7
\]
- Answer: \( \boxed{7} \)

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14) A plane journey takes 6 \( \frac{1}{2} \) hours. If I set off at 8:40 am, what time will I arrive?

- Convert 6 \( \frac{1}{2} \) hours to minutes:
\[
6 \frac{1}{2} \text{ hours} = 6 \times 60 + 30 = 390 \text{ minutes}
\]
- Add 390 minutes to 8:40 am:
- 8:40 am + 390 minutes:
- 390 minutes = 6 hours and 30 minutes.
- 8:40 am + 6 hours = 2:40 pm.
- 2:40 pm + 30 minutes = 3:10 pm.
- Answer: \( \boxed{3:10 \text{ pm}} \)

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15) A pen costs £4.60. How much will 2 pens cost?

- Multiply the cost of one pen by 2:
\[
4.60 \times 2 = 9.20
\]
- Answer: \( \boxed{£9.20} \)

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16) A piece of rope measuring 4m is cut into 8 equal lengths. How long will each piece be?

- Divide the total length by the number of pieces:
\[
\frac{4}{8} = 0.5 \text{ meters}
\]
- Answer: \( \boxed{0.5 \text{ m}} \)

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Final Answers:

1. \( \boxed{1.5} \)
2. \( \boxed{37} \)
3. \( \boxed{\frac{3}{6}} \)
4. \( \boxed{7} \)
5. \( \boxed{18,027} \)
6. \( \boxed{80} \)
7. \( \boxed{5 \text{ and } 4} \)
8. \( \boxed{4} \)
9. \( \boxed{1, 3, 5, 15} \)
10. \( \boxed{5.09} \)
11. \( \boxed{£7.30} \)
12. \( \boxed{10} \)
13. \( \boxed{7} \)
14. \( \boxed{3:10 \text{ pm}} \)
15. \( \boxed{£9.20} \)
16. \( \boxed{0.5 \text{ m}} \)