What is the sum of all interior angles of a triangle?
★ This is a theorem — true for EVERY triangle, always.
$\angle A + \angle B + \angle C = ?°$
🧠TRIANGLE SUM — always 180°, no exceptions
Answer
PROBLEM 13
Pythagorean Theorem
Find the hypotenuse.
★ \(c\) is always the LONGEST side, opposite the right angle.
Right triangle: legs \(a = 3\), \(b = 4\). Find \(c\).
🧠a² + b² = c² — "3-4-5" is the classic triple!
c =
PROBLEM 14
Perimeter
Find the perimeter of the rectangle.
★ Perimeter = total distance AROUND the shape (add all sides).
Rectangle: length \(= 10\), width \(= 4\)
🧠P = 2l + 2w — "two lengths + two widths"
P =
PROBLEM 15
Area of Triangle
Find the area.
★ Don't forget to divide by 2! Triangles = half a rectangle.
Triangle: base \(= 8\), height \(= 6\)
🧠A = ½ bh — half times base times height
A =
PROBLEM 16
Quadrilateral Angles
What is the sum of interior angles in a quadrilateral?
★ Each time you add a side to a polygon, add 180° to the total.
Square, rectangle, trapezoid — what's the angle sum?
🧠(n − 2) × 180° — n = number of sides · quad: (4−2)×180
Sum =
PROBLEM 17
Circumference of Circle
Find the circumference. Use \(\pi \approx 3.14\).
★ C uses diameter (full width); Area uses radius (half width). Confusing these = #1 mistake!
Circle with diameter \(d = 24\)
🧠C = πd (diameter) or C = 2πr (radius)
C ≈
PROBLEM 18
Congruence vs. Similarity
Choose the correct word:
Two triangles have exactly the same shape AND the same size. They are _____.
★ Similar = same shape, different size. Congruent = same shape AND size.
Same shape + Same size = ?
🧠≅ CONGRUENT (identical) · ~ SIMILAR (proportional copy)
Word
PROBLEM 19
Parallel Lines & Transversals
Find the missing angle.
★ Alternate interior angles are EQUAL. Co-interior (same-side) angles add to 180°.
Two parallel lines cut by a transversal. One alternate interior angle = 70°. Find its alternate interior partner.