3 boys and 7 girls can complete John work in 10 days . But 4 boys and 6 girls need 8 days to complete the same work . In how many days will 10 girls complete the same work?  Choose the correct choice from the following answers:
A) 30 days	B) 35 days	C) 40 days	D) 50 days	E) 60 days
Work done by 4 boys and 6 girls in 1 day = 1/8   Work done by 3 boys and 7 girls in 1 day = 1/10   Let 1 man does m work in 1 day and 1 woman does w work in 1 day. The above equations can be written as   4m + 6w = 1/8 ---(1)   3m + 7w = 1/10 ---(2)   Solving equation (1) and (2) , we get m=11/400 and w=1/400   Amount of work 10 girls can do in John day = 10 × (1/400) = 1/40   Ie, 10 girls can complete the work in 40 days   40 days
<result>C</result>
3 boys and 7 girls can complete John work in 10 days . But 4 boys and 6 girls need 8 days to complete the same work . In how many days will 10 girls complete the same work?