Page 1
Similarity
Practice Set 1.1
Q. 1. Base of a triangle is 9 and height is 5. Base of another triangle is 10 and
height is 6. Find the ratio of areas of these triangles.
Answer : We know that area of triangle = × Base× Height
? Area (triangle 1) = ×9× 5
=
? Area (triangle 2) = ×10× 6
= 30
? The ratio of areas of these triangles will be =
=
=
=
Q. 2. If figure 1.13 BC ? AB, AD ? AB, BC = 4, AD = 8, then find
?? (??????? )
?? (??????? )
.
Page 2
Similarity
Practice Set 1.1
Q. 1. Base of a triangle is 9 and height is 5. Base of another triangle is 10 and
height is 6. Find the ratio of areas of these triangles.
Answer : We know that area of triangle = × Base× Height
? Area (triangle 1) = ×9× 5
=
? Area (triangle 2) = ×10× 6
= 30
? The ratio of areas of these triangles will be =
=
=
=
Q. 2. If figure 1.13 BC ? AB, AD ? AB, BC = 4, AD = 8, then find
?? (??????? )
?? (??????? )
.
Answer : Here, ?ABC and ?ADB has common Base.
?
(PROPERTY: Areas of triangles with equal bases are proportional to their
corresponding heights.)
?
=
=
Q. 3. In adjoining figure 1.14 seg PS ? seg RQ, seg QT ? seg PR. If RQ = 6, PS = 6
and PR = 12, then find QT.
Answer :
Considering, Area of (?PQR) with base QR
? PS will be the Height
Page 3
Similarity
Practice Set 1.1
Q. 1. Base of a triangle is 9 and height is 5. Base of another triangle is 10 and
height is 6. Find the ratio of areas of these triangles.
Answer : We know that area of triangle = × Base× Height
? Area (triangle 1) = ×9× 5
=
? Area (triangle 2) = ×10× 6
= 30
? The ratio of areas of these triangles will be =
=
=
=
Q. 2. If figure 1.13 BC ? AB, AD ? AB, BC = 4, AD = 8, then find
?? (??????? )
?? (??????? )
.
Answer : Here, ?ABC and ?ADB has common Base.
?
(PROPERTY: Areas of triangles with equal bases are proportional to their
corresponding heights.)
?
=
=
Q. 3. In adjoining figure 1.14 seg PS ? seg RQ, seg QT ? seg PR. If RQ = 6, PS = 6
and PR = 12, then find QT.
Answer :
Considering, Area of (?PQR) with base QR
? PS will be the Height
Now, consider the Area of (?PQR) with base PR
? QT will be the Height
? The triangle is the same
? The area will be the same irrespective of the base taken.
And we know that area of triangle = × Base× Height
? ×QR×PS
= × PR × QT
? × 6 × 6
= × 12 × QT
? QT = 3
Q. 4. In adjoining figure, AP ? BC, AD || BC, then find A(?ABC) : A (?BCD)
Answer :
Page 4
Similarity
Practice Set 1.1
Q. 1. Base of a triangle is 9 and height is 5. Base of another triangle is 10 and
height is 6. Find the ratio of areas of these triangles.
Answer : We know that area of triangle = × Base× Height
? Area (triangle 1) = ×9× 5
=
? Area (triangle 2) = ×10× 6
= 30
? The ratio of areas of these triangles will be =
=
=
=
Q. 2. If figure 1.13 BC ? AB, AD ? AB, BC = 4, AD = 8, then find
?? (??????? )
?? (??????? )
.
Answer : Here, ?ABC and ?ADB has common Base.
?
(PROPERTY: Areas of triangles with equal bases are proportional to their
corresponding heights.)
?
=
=
Q. 3. In adjoining figure 1.14 seg PS ? seg RQ, seg QT ? seg PR. If RQ = 6, PS = 6
and PR = 12, then find QT.
Answer :
Considering, Area of (?PQR) with base QR
? PS will be the Height
Now, consider the Area of (?PQR) with base PR
? QT will be the Height
? The triangle is the same
? The area will be the same irrespective of the base taken.
And we know that area of triangle = × Base× Height
? ×QR×PS
= × PR × QT
? × 6 × 6
= × 12 × QT
? QT = 3
Q. 4. In adjoining figure, AP ? BC, AD || BC, then find A(?ABC) : A (?BCD)
Answer :
We can re-draw the fig. 1.15 (as shown above) where we add DO
Which will be height of ?BCD.
Now,
(PROPERTY: Areas of triangles with equal bases are proportional to their
corresponding heights.)
?
?
(? the distance between the two parallel lines is always equal ? AP = DO)
? = 1:1
Q. 5. In adjoining figure PQ ? BC, AD ? BC then find following ratios.
Page 5
Similarity
Practice Set 1.1
Q. 1. Base of a triangle is 9 and height is 5. Base of another triangle is 10 and
height is 6. Find the ratio of areas of these triangles.
Answer : We know that area of triangle = × Base× Height
? Area (triangle 1) = ×9× 5
=
? Area (triangle 2) = ×10× 6
= 30
? The ratio of areas of these triangles will be =
=
=
=
Q. 2. If figure 1.13 BC ? AB, AD ? AB, BC = 4, AD = 8, then find
?? (??????? )
?? (??????? )
.
Answer : Here, ?ABC and ?ADB has common Base.
?
(PROPERTY: Areas of triangles with equal bases are proportional to their
corresponding heights.)
?
=
=
Q. 3. In adjoining figure 1.14 seg PS ? seg RQ, seg QT ? seg PR. If RQ = 6, PS = 6
and PR = 12, then find QT.
Answer :
Considering, Area of (?PQR) with base QR
? PS will be the Height
Now, consider the Area of (?PQR) with base PR
? QT will be the Height
? The triangle is the same
? The area will be the same irrespective of the base taken.
And we know that area of triangle = × Base× Height
? ×QR×PS
= × PR × QT
? × 6 × 6
= × 12 × QT
? QT = 3
Q. 4. In adjoining figure, AP ? BC, AD || BC, then find A(?ABC) : A (?BCD)
Answer :
We can re-draw the fig. 1.15 (as shown above) where we add DO
Which will be height of ?BCD.
Now,
(PROPERTY: Areas of triangles with equal bases are proportional to their
corresponding heights.)
?
?
(? the distance between the two parallel lines is always equal ? AP = DO)
? = 1:1
Q. 5. In adjoining figure PQ ? BC, AD ? BC then find following ratios.
Answer : We know that area of triangle = × Base × Height
(i)
(PROPERTY: Areas of triangles with equal heights are proportional to their
corresponding bases.)
(ii)
(PROPERTY: Areas of triangles with equal bases are proportional to their
corresponding heights.)
(iii)
(PROPERTY: Areas of triangles with equal heights are proportional to their
corresponding bases.)
(iv)
=
Practice Set 1.2
Q. 1. Given below are some triangles and lengths of line segments. Identify in
which figures, ray PM is the bisector of ?OPR.
Answer :
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