F _ _ R
B R _ T H _ R S
_ N D
T H R _ _
S _ S T _ R S .
E V _ R Y
B _ Y
W _ L L
H _ V _
3
B R _ T H _ R S
_ N D
3
S _ S T _ R S .
E V _ R Y
G _ R L
W _ L L
H _ V _
4
B R _ T H _ R S
_ N D
2
( H _ L F
_ F
T H _
N _ M B _ R
_ F
B R _ T H _ R S )
S _ S T _ R S Clue
THREE SISTERS AND TWO BROTHERS. THIS CAN BE SOLVED BY SIMPLE DEDUCTION, BUT IF ALGEBRA IS USED LET X BE THE NUMBER OF SISTERS AND Y THE NUMBER OF BROTHERS: X+ 1= 2Y Y+ 1= X THEREFORE, Y + 1+ 1= 2Y SO Y =2 OR X + 1= 2X - 2 SO X = 3 THE BOOK COSTS $2. LET THE COST BE X. WE KNOW THAT: X = 1 + X/2 SOLVING FOR X WILL GIVE 2 THEY ARE 10.5 AND 0.5 YEARS OLD. A COMMON WRONG ANSWER IS 10 AND 1. THIS IS WRONG BECAUSE THE DIFFERENCE IN AGE WOULD BE 9, NOT 10 FOUR BROTHERS AND THREE SISTERS. EVERY BOY WILL HAVE 3 BROTHERS AND 3 SISTERS. EVERY GIRL WILL HAVE 4 BROTHERS AND 2 (HALF OF THE NUMBER OF BROTHERS) SISTERS