Checkpoint: formulas, calendars and slips

A regular triangle has sides of 9 cm. Which formula and value are right?

• 3a, so 27 cm
• 3 + a, so 12 cm
• a ÷ 3, so 3 cm

The two diagonals of a calendar square each add to 54. What is the top-left date?

• 46
• 23
• 27

A plus of five calendar dates adds to 95. What is its middle date?

• 47
• 90
• 19

Which line is right?

• 7 − (2 + b) = 5 − b
• 7 − (2 + b) = 5 + b
• 7 − (2 + b) = 9 − b