question_answer

A roll of thread 907i cm long is cut into 5 parts to make up 5 circles as shown in the figure. The radii of the circles increase by 1 cm consecutively. Find the radius of the smallest circle.

A)  7 cm                                     

B)  5 cm

C)  6 cm                     

D)         9 cm

Correct Answer: A

Solution :

Circumference of 5 circles \[~(\text{2}\times \text{52}\times \text{73) cm}\] \[=(\text{25}\times \text{7})\text{(2}\times {{\text{5}}^{\text{2}}}\times {{\text{7}}^{\text{3}}}\text{) c}{{\text{m}}^{\text{2}}}\] \[={{\text{2}}^{\text{6}}}\times {{\text{5}}^{\text{2}}}\times {{\text{7}}^{\text{4}}}\text{c}{{\text{m}}^{\text{2}}}\]                \[2-\sqrt{4}=2-2=0\] \[{{(\sqrt{5})}^{2}}=5\]Radius of the smallest circle, r = 7 cm.