Place in the grid 21 circles and fi ll them with symbols "X", "+" and "Y". There must be exactly 7 instances of each symbol. Same symbols cannot be in one row or one column. Cells with circles must not touch each other, not even diagonally. Some circles are already placed. Digit near the circle shows the number of other circles, pointed by symbol in the circle. "X" points on the circles in the same diagonal, "Y" points on the circles higher in the same diagonal and on the circles lower in the same column, "+" points on the circles in the same row and column.
Example:
Answer key: write down the sums of all the digits, which must be near the same symbols in order "X", "+", "Y". For the example the answer would be: 2, 8, 4.
Answer:
18, 20, 5
Using the complete domino set and following the domino rules build in the grid closed single chain, not touching itself even diagonally. Numbers outside the grid show all the values of halfdominoes in corresponding rows and columns. Grey rectangles show the placement of all "doubles".
Answer key: write down all horizontally oriented dominoes, in order from top to bottom, from left to right.
Answer:
6-3, 4-1, 2-6, 2-5, 0-5, 5-3, 3-4, 4-0, 0-0, 0-3, 1-1, 6-0, 1-6, 2-1, 5-6, 4-4, 5-5
Place in the grid complete pentamino set without overlapping. Elements can be rotated and/or mirrored. Your goal is to leave uncovered the fewest number of grey cells.
Answer key: describe the table row by row, from top to bottom, replacing empty cells with symbol "-". Best answer brings 8 points; each next answer will bring two points less.