Keystones Lintel — Jan 26 - Feb 1

Monday 26 January 2026

Keystones #26 · Five questions · Open this day only

1. Number

A value is 94.5 (to dp). State the error interval

Answer: 94.45 ≤ x < 94.55
2. Algebra

Expand: (x - 5)(x - 3)

Answer: x² - 8x + 15
3. Geometry

Calculate the area of a circle with diameter 15cm

Answer: 176.71cm²
4. Ratio

48 out of 91 students passed. What percentage passed?

Answer: 52.7%
5. Statistics

Find the mean, median and range of: 76, 22, 78, 92, 44, 17, 94, 79, 63

Answer: Mean = 62.8, Median = 76, Range = 77

Keystones #27 · Five questions · Open this day only

1. Number

30 is rounded to the nearest integer. What is the error interval?

Answer: 29.5 ≤ x < 30.5
2. Algebra

Expand: (x + 6)(x - 3)

Answer: x² + 3x - 18
3. Geometry

A circle has area 153.9cm². Find its radius (dp)

Answer: 7cm
4. Ratio

51 out of 82 students passed. What percentage passed?

Answer: 62.2%
5. Statistics

Find the mean, mode, median and range of: 43, 15, 30, 17, 30

Answer: Mean = 27, Mode = 30, Median = 30, Range = 28

Keystones #28 · Five questions · Open this day only

1. Number

84 is rounded to the nearest integer. What is the error interval?

Answer: 83.5 ≤ x < 84.5
2. Algebra

Expand: (x + 7)(x - 6)

Answer: x² + x - 42
3. Geometry

A circle has area 314.2cm². Find its radius (dp)

Answer: 10cm
4. Ratio

46 out of 70 students passed. What percentage passed?

Answer: 65.7%
5. Statistics

Find the mean, mode, median and range of: 15, 36, 36, 16, 39

Answer: Mean = 28.4, Mode = 36, Median = 36, Range = 24

Keystones #29 · Five questions · Open this day only

1. Number

A value is 18.9 (to dp). State the error interval

Answer: 18.85 ≤ x < 18.95
2. Algebra

Expand: (x - 5)(x - 6)

Answer: x² - 11x + 30
3. Geometry

Calculate the area of a circle with diameter 11cm

Answer: 95.03cm²
4. Ratio

47 out of 91 students passed. What percentage passed?

Answer: 51.6%
5. Statistics

Find the mean, median and range of: 70, 40, 87, 14, 60, 72, 22, 72, 27

Answer: Mean = 51.6, Median = 60, Range = 73

Keystones #30 · Five questions · Open this day only

1. Number

A value is 74.8 (to dp). State the error interval

Answer: 74.75 ≤ x < 74.85
2. Algebra

Expand: (x + 7)(x - 8)

Answer: x² -x - 56
3. Geometry

A circle has area 201.cm². Find its radius (dp)

Answer: 8cm
4. Ratio

52 out of 80 students passed. What percentage passed?

Answer: 65%
5. Statistics

Find the mean, median and range of: 39, 98, 61, 32, 77, 18, 86, 66, 48

Answer: Mean = 58.3, Median = 61, Range = 80