Question 8
Find the missing number.
a) Three central squares with surrounding numbers (top, left, right, bottom; centre): (12, 18, 3, 12; 45), (19, ?, 13, 12; 55), (4, 8, 9, 3; 24).
b) 4 × 4 grid rows: [88, 35, 10, 1]; [35, 20, 7, 2]; [10, ?, 4, 1]; [1, 2, 1, 2].
c) Three 2 × 2 grids, rows top to bottom: [24, 11; 89, 76], [8, 6; 94, 92], [10, 15; ?, 90].
Complete matching diagram from the supplied Grades 8–9 duplicate, physical PDF page 33; recovery details are in the solution.
**Editorial input note:** Enter the missing numbers for (a), (b), and (c), in order, separated by semicolons with no spaces.
a) Three central squares with surrounding numbers (top, left, right, bottom; centre): (12, 18, 3, 12; 45), (19, ?, 13, 12; 55), (4, 8, 9, 3; 24).
b) 4 × 4 grid rows: [88, 35, 10, 1]; [35, 20, 7, 2]; [10, ?, 4, 1]; [1, 2, 1, 2].
c) Three 2 × 2 grids, rows top to bottom: [24, 11; 89, 76], [8, 6; 94, 92], [10, 15; ?, 90].
Complete matching diagram from the supplied Grades 8–9 duplicate, physical PDF page 33; recovery details are in the solution.
**Editorial input note:** Enter the missing numbers for (a), (b), and (c), in order, separated by semicolons with no spaces.