Overestimating vs underestimating | Maths | Quizalize & Oak National Academy

Starter quiz

__________ are the digits in a number that contribute to the accuracy of the number. The first significant figure is the first non-zero digit.
- Estimated numbers
- Important number
- Real numbers
- Significant figures ✓
Which of the following are good, quick estimate calculations for 577 ÷ 19.57?
- 580 ÷ 20 ✓
- 600 ÷ 20 ✓
- 580 ÷ 19.5
- 600 ÷ 19.5
Which of the following are correct for ${11.239\times3.12}\over{0.488}$ ?
- ${11\times3} \over {0.5}$ $= 16.5$
- ${10\times3} \over {0.5}$ $= 15$
- ${11\times3} \over {0.5}$ $= 66$ ✓
- ${10\times3} \over {0.5}$ $= 60$ ✓
Match each calculation to its approximate answer.
- $\frac{9.8}{0.120}$
  
  ⇔
  
  $100$ ✓
- $\frac{98}{0.111}$
  
  ⇔
  
  $1000$ ✓
- $\frac{9.8}{0.2003}$
  
  ⇔
  
  $50$ ✓
- $\frac{980}{0.199}$
  
  ⇔
  
  $5000$ ✓
- $\frac{980}{0.498}$
  
  ⇔
  
  $2000$ ✓
- $\frac{9}{0.51}$
  
  ⇔
  
  $18$ ✓
A square plot of grass has a length of 7.88 m (2 d.p). Select the correct estimate for the area of the square grass plot.
- 8 × 8 = 64 m² ✓
- 8 × 8 = 16 m²
- 8 + 8 + 8 + 8 = 32 m²
- 8 + 8 + 8 + 8 = 32 m
Izzy thinks of a number. Truncated to 1 s.f., it is 500. Rounded to the nearest 50, it is 600. It is multiple of 5 and a palindrome . All of its digits are prime numbers. Izzy's number is ______
- '575' ✓