Find the fourth proportional to :
(i) 3, 8 and 21
(ii) 1.4, 3.2 and 7
(iii) 1.5, 4.5 and 3.6
(iv) a², ab and b²
(v) (a² − ab + b²), (a³ + b³) and (a − b)

Question

Find the fourth proportional to : (i) 3, 8 and 21 (ii) 1.4, 3.2 and 7 (iii) 1.5, 4.5 and 3.6 (iv) a2, ab and b2 (v) (a2 − ab + b2), (a3 + b3) and (a − b)

KnowledgeBoat · Accepted Answer

(i) Given, 3, 8 and 21 Let the fourth proportional to 3, 8 and 21 be x, ⇒ 3 : 8 = 21 : x Hence, the fourth proportional is 56. (ii) Given, 1.4, 3.2 and 7 Let the fourth proportional to 1.4, 3.2 and 7 be x, ⇒ 1.4 : 3.2 = 7 : x Hence, the fourth proportional is 16. (iii) Given, 1.5, 4.5 and 3.6 Let the fourth proportional to 1.5, 4.5 and 3.6 be x, ⇒ 1.5 : 4.5 = 3.6 : x Hence, the fourth proportional is 10.8. (iv) Given, a2, ab and b2 Let the fourth proportional to a2, ab and b2 be x, ⇒ a2 : ab = b2 : x Hence, the fourth proportional is . (v) Given, (a2 − ab + b2), (a3 + b3) and (a − b) Let the fourth proportional to (a2 − ab + b2), (a3 + b3) and (a − b) be x, ⇒ a2 : ab = b2:x Hence, the fourth proportional is a2 - b2.

Mathematics

Find the fourth proportional to :
(i) 3, 8 and 21
(ii) 1.4, 3.2 and 7
(iii) 1.5, 4.5 and 3.6
(iv) a², ab and b²
(v) (a² − ab + b²), (a³ + b³) and (a − b)

Ratio Proportion

Related Questions

If (3a + 2b) : (5a + 3b) = 18 : 29, find (a : b).

Find x, when :
(i) 3 : 4 :: 2.4 : x
(ii) 1 : 3 :: x : 7
(iii) x : 1.5 :: 3 : 5

Mathematics

Find the fourth proportional to :(i) 3, 8 and 21(ii) 1.4, 3.2 and 7(iii) 1.5, 4.5 and 3.6(iv) a2, ab and b2(v) (a2 − ab + b2), (a3 + b3) and (a − b)

Ratio Proportion

Related Questions

If (3a + 2b) : (5a + 3b) = 18 : 29, find (a : b).

Find x, when :(i) 3 : 4 :: 2.4 : x(ii) 1 : 3 :: x : 7(iii) x : 1.5 :: 3 : 5

Find the fourth proportional to :
(i) 3, 8 and 21
(ii) 1.4, 3.2 and 7
(iii) 1.5, 4.5 and 3.6
(iv) a², ab and b²
(v) (a² − ab + b²), (a³ + b³) and (a − b)

Find x, when :
(i) 3 : 4 :: 2.4 : x
(ii) 1 : 3 :: x : 7
(iii) x : 1.5 :: 3 : 5