No, he is not correct because of the total of 6 triangles 4 are blue.
ie \(\frac { 4 }{ 6 } \)^th triangles are blue.

Product of extremes = 6 \(\times\) 15 = 90
\(\therefore\) Product of means = 90 = 1 \(\times\) 90
The required sets are 1 and 30, 2 and 45, 3 and 30, 5 and 18, 6 and 15, 9 and 10
= 1 \(\times\) 90
= 2 \(\times\)45
= 3 \(\times\) 30
= 5 \(\times\) 18
= 6 \(\times\) 15
= 9 \(\times\) 10
So, 6 : 1 : : 90 : 15.

36 inches, 6 Feet

Step 1: Write the ratio in fraction form as\(20\over 5\).
Step 2: Divide each quantity by 5. That is, \({20\div 5\over 5\div 5}={4\over1}=4:1\)
This is the ratio in the simplest form.

7 : 15
Fraction = \(​​\frac {7 \div 1}{15 \div 1}=\frac{7}{15}\)
Simplest form = 7 : 15

Teacher to Student ratio of 6^th Std = 6 : 12 = \(\frac{6}{12}=\frac{1}{2}\) = 1 : 2
Teacher to Student ratio of 7^th Std = 9 : 27 = \(\frac{9}{27}=\frac{1}{3}\) = 1 : 3
Teacher to Student ratio of 8^th Std = 4 : 16 = \(\frac{4}{16}=\frac{1}{4}\) = 1 : 4
In standard 8th the ratio of teacher to Student is 1 : 4 and which is the least.

(i) \(\frac { Speed\quad of\quad the\quad Elephant }{ Speed\quad of\quad the\quad Lion } =\frac { 20 }{ 80 } =\frac { 1 }{ 4 } \) ⇒ 1:4
(ii) \(\frac { Speed\quad of\quad the\quad Lion }{ Speed\quad of\quad the\quad Cheetah } =\frac { 80 }{ 100 } =\frac { 4 }{ 5 } \)⇒ 4:5
(iii) \(\frac { Speed\quad of\quad the\quad Elephant }{ Speed\quad of\quad the\quad Cheetah } =\frac { 20 }{ 100 } =\frac { 1 }{ 5 } \)⇒ 1:5
(iv) Ratio of Elephant to Cheetah is the least.

(i) 78 :130 : : 12:20
Extreme terms are 78 and 20. Mean terms are 130 and 12.
Product of Extremes = 78 \(\times\) 20 = 1560
Product of Means = 130 \(\times\) 12 = 1560
Product of Extremes = Product of means
∴ It is in proportion.
(ii) 400 : 50 : : 25 : 625
Product of extremes = 400 \(\times\) 625 = 250,000
Product of means = 50 \(\times\) 25 = 1250
Here product of extremes ≠ product of means
∴ 400 : 50 and 25 : 625 are not in proportion

\(3:4=\frac{3}{4}\times\frac{2}{2}=\frac{6}{8}\)
\(7:8=\frac{7}{8}\)
Here \(\frac{7}{8}\) larger than \(\frac{6}{8}\)
\(\therefore\) 7 : 8 larger than 3 : 4

Parking cost of bicycle = Rs. 5
Parking cost of Scooter = Rs. 15
\(\frac { Parking\ cost\ of\ bicycle }{ Parking\ cost\ of\ scooter } =\frac { 5 }{ 15 } =\frac { 1 }{ 3 } \)
Parking cost of bicycle : scooter = 1 : 3

(a) green balls = 4, Yellow balls = 3, black balls =  5.
so, Black balls
(b) 5 parts of Black balls = 40 balls
\(\therefore \) 1 part of Black balls = \(\frac{40}{5}=8 \text { balls }\)
4part of Green balls = 4 \(\times\) 8 = 32
3 part of yellow balls = 3 \(\times\) 8 = 24
If there are 40 black balls, then total number of balls = 32 + 24 + 40 = 96 balls
(c) Number of green balls = 32
Number of Yellow balls = 24

The given pictures are in the ratio 2 : 5 and 4 : 3 respectively.
Here the extremes are 2 and 3 and the means are 5 and 4.
Product of extremes, ad = 2 \(\times\)3 = 6.
Product of means, bc = 5 \(\times\) 4 = 20.
Thus, we find ad\(\neq\)  bc and hence 2 : 5 and 4 : 3 are not in proportion.