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Tips on Solving Logic Problems - a logic problem
Five sisters all have their birthday in a different month and each on a different day of the week. Using the clues below, determine the month and day of the week each sister's birthday falls.
HOW TO SOLVE IT:
The grids provided to help solve logic problems are useful for identifying what you have learned from each clue. Where the vertical and horizontal squares meet are your possible answers and these will be crossed out as each is proven to be false. When you find a true match, draw a black dot in the appropriate square. When you prove a combination false, draw an 'x' in the square.
Clue 1: The first clue states that Paula was born in March so
put a black dot in the square for "Paula" and "March" as shown. Since
Paula was born in March, none of the other possibilities are valid, so the
rest of the row and column can be marked with an 'x' as shown. The clue
also states that Paula's birthday is not on Saturday, thus "Saturday" for
"Paula" can also be crossed out as shown. The second half of the clue
states that Abigail's birthday is not on Wednesday or Friday so you can
mark Wednesday and Friday for Abigail with an 'x' in the right section of
the grid as shown.
Clue 2: According to the second clue, Brenda and Mary could not
have been born in February since the girl whose birthday is Monday was
born earlier in the year. Likewise, Brenda and Mary didn't have a birthday
on Monday. So these squares can be crossed out. Also, in the bottom part
of the grid, the Monday birthday cannot happen in July or December because
both Brenda and Mary had birthdays AFTER the girl whose birthday is on
Monday so these two squares can also be crossed out as shown.
Clue 3: Tara was not born in February and so that square is
crossed out. Now the only square in that row that isn't crossed out is
Abigail. By elimination therefore, Abigail was born in February. Put a
black dot in that square and cross out the rest of the horizontal row. In
addition, since you know from clue 1 that Abigail's birthday is not on a
Friday or a Wednesday and you know she was born in February, you can cross
out Wednesday and Friday in the bottom block of the grid for February.
Also, from the second half of Clue 3, Tara's birthday is on the weekend,
so Monday, Wednesday, and Friday are crossed out for Tara in the right
section of the grid as shown.
Clue 4: Mary wasn't born in December so cross it out as shown.
Since her birthday isn't on a weekday, you can also cross out Wednesday
and Friday for Mary in the right-hand section of the grid. From Clue 2 you
know that Tara's birthday was on a weekend too. So in the right section of
the grid, Saturday and Sunday can be crossed out for Abigail, Brenda, and
Paula. This leaves only Monday for Abigail to put a black dot in this
square and cross out the rest of the column for Monday. From the last part
of Clue 4, in the bottom section of the grid, put a dot for June and
Sunday, crossing out the rest of the column and row respectively as shown.
Also, in the upper grid, cross out Brenda for June because you know her
birthday wasn't on the weekend.
Clue 5: Since Tara was born before Brenda, cross out December
for Tara since she couldn't have been born last. This leaves only December
for Brenda so put a black dot in that square and cross out the rest of the
row. From the second half of the clue, you know that mary wasn't born in
July so by elimination Tara was born in July. Put a black dot in that
square and cross out the rest of the row. Also put a black dot in the
square for Mary and June since it's the last square open. You've now
determined all of the months in which everyone was born. Also, since you
know that June goes with Sunday and Mary was born in June, her birthday is
on Sunday so mark that off in the right section of the grid. This then
leaves Tara for Saturday so mark that too. Lastly, from the clue, Brenda's
birthday wasn't on Friday. So by elimination, Brenda's birthday was on
Wednesday and Paula's birthday was on Friday.
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