Naiakea Special EducationWarm-up ProblemToshi, a bird-watcher, saw a group of birds. He noticed the following:There were 4 types of birds.Two-sevenths of the group were sparrows.Three-fifths of the rest were mynahs.One-half of the birds that were neither sparrows nor mynahs were cardinals.All the rest were doves; there were four dovesHow many mynahs did Toshi see?Hilo-Waiakea Special Education
Q. Naiakea Special EducationWarm-up ProblemToshi, a bird-watcher, saw a group of birds. He noticed the following:There were 4 types of birds.Two-sevenths of the group were sparrows.Three-fifths of the rest were mynahs.One-half of the birds that were neither sparrows nor mynahs were cardinals.All the rest were doves; there were four dovesHow many mynahs did Toshi see?Hilo-Waiakea Special Education
Assume total number of birds: Let's assume the total number of birds is x.
Calculate sparrows: Calculate the number of sparrows, which is two-sevenths of the group.Sparrows = (72)×x
Find birds not sparrows: Find the number of birds that are not sparrows.Not sparrows = x - SparrowsNot sparrows = x−(72)×x
Calculate mynahs: Calculate the number of mynahs, which is three-fifths of the birds that are not sparrows.Mynahs = (53)×Not sparrowsMynahs = (53)×(x−(72)×x)
Calculate birds neither sparrows nor mynahs: Calculate the number of birds that are neither sparrows nor mynahs.Neither = Not sparrows - MynahsNeither = (x−(72)⋅x)−(53)⋅(x−(72)⋅x)
Calculate cardinals: Half of the birds that are neither sparrows nor mynahs are cardinals.Cardinals = (21)×NeitherCardinals = (21)×((x−(72)×x)−(53)×(x−(72)×x)))
Determine number of doves: The rest of the birds are doves, and there are 4 doves.Doves =4
Set up equation for x: Set up the equation to find x using the information about doves.Doves = Neither - Cardinals4=((x−(72)⋅x)−(53)⋅(x−(72)⋅x))−(21)⋅((x−(72)⋅x)−(53)⋅(x−(72)⋅x))
More problems from Percents of numbers: word problems