Introduction to Algebra
Class 6 — Solutions Key
- 9 - 1 = 8
- 98 - 21 = 77
- 987 - 321 = 666
- 9876 - 4321 = 5555
- 98765 - 54321 = 44444
What comes next?
The next pattern step subtracts the next sequence digit block:
987654 - 654321 = 333333
Explanation: Each successive step appends the next decreasing integer to the minuend, the next increasing integer to the subtrahend, and yields a repeating sequence of a digit decremented by 1 compared to the previous step.
Total length of wire = 12s cm
(i) An equilateral triangle:
- An equilateral triangle has 3 equal sides.
- Length of each side = Total length / 3 = 12s / 3 = 4s cm.
(ii) A square:
- A square has 4 equal sides.
- Length of each side = Total length / 4 = 12s / 4 = 3s cm.
Step 1: Formulate equations to solve for the shapes.
Let Star = x, Smile = y, and Triangle = z.
From Row 1: x + y + y + x = 30 ⇒ 2x + 2y = 30 ⇒ x + y = 15
From Column 1: x + x + x + x = 32 ⇒ 4x = 32 ⇒ x (Star) = 8
Substitute x = 8 into x + y = 15 ⇒ 8 + y = 15 ⇒ y (Smile) = 7
From Row 2: x + x + z + z = 36 ⇒ 2x + 2z = 36 ⇒ 2(8) + 2z = 36 ⇒ 16 + 2z = 36 ⇒ 2z = 20 ⇒ z (Triangle) = 10
Step 2: Calculate missing totals.
- Row 3 total: Star + Triangle + Smile + Smile = 8 + 10 + 7 + 7 = 32
- Row 4 total: Star + Smile + Triangle + Smile = 8 + 7 + 10 + 7 = 32
- Col 2 total: Smile + Star + Triangle + Smile = 7 + 8 + 10 + 7 = 32
- Col 3 total: Smile + Triangle + Smile + Triangle = 7 + 10 + 7 + 10 = 34
- Col 4 total: Star + Triangle + Smile + Smile = 8 + 10 + 7 + 7 = 32
- Grand Total (Diagonal): 32 + 32 + 34 + 32 = 130
| Star (8) | Smile (7) | Smile (7) | Star (8) | = 30 |
| Star (8) | Star (8) | Triangle (10) | Triangle (10) | = 36 |
| Star (8) | Triangle (10) | Smile (7) | Smile (7) | = 32 |
| Star (8) | Smile (7) | Triangle (10) | Smile (7) | = 32 |
| = 32 | = 32 | = 34 | = 32 | = 130 |
Rule: Total Matches Played = Matches Won + Matches Lost
- For Team C: n = 4 + 6 ⇒ n = 10
- For Team D: a = 7 + 2 ⇒ a = 9
- For Team E: 9 = b + 3 ⇒ b = 9 - 3 ⇒ b = 6
- For Team F: 10 = 6 + c ⇒ c = 10 - 6 ⇒ c = 4
- For Team G: 8 = x + 4 ⇒ x = 8 - 4 ⇒ x = 4
- For Team H: y = 3 + 6 ⇒ y = 9
- For Team A (lost matches 'x'): Note: Team G already uses variable 'x'. To solve the entry under Team A, 8 = 5 + k (where k is the variable represented in the table as a modified 'x') ⇒ variable = 3
- For Team B (lost matches 'y'): Note: Team H already uses variable 'y'. To solve the entry under Team B, 7 = 6 + m (where m is the variable represented in the table as a modified 'y') ⇒ variable = 1
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