Two varieties of steel, A and B, have a ratio of iron to chromium as 5:1 and 7:2, respectively. Steel C is produced by mixing alloys A and B at a ratio of 3:2. What is the ratio of iron to chromium in C?  Choose the correct option:	A) 17 : 73	B) 78 : 14	C) 45 : 30	D) 73 : 17	E) 4 : 9

Rationale: in 6 parts of alloy a , 5 parts are iron , and 1 part is chromium . in 9 parts of alloy b , 7 parts are iron and 2 parts are chromium . first , to compare the two alloys , get the same number of parts in total - we can use 18 . so we have : in 18 parts of alloy a , 15 parts are iron and 3 are chromium . in 18 parts of alloy b , 14 parts are iron and 4 are chromium . so combining 3 of a with 2 of b , we ' d be combining 45 and 28 parts of iron , or 73 parts of iron , with 9 and 8 of chromium , or 17 of chromium , so 73 to 17 is the answer . answer : d
Answer: D