Four milliliters of ink A is added to 10 milliliters of ink B, forming a mixture of inks. Ink A contains 10 percent blue pigment. Ink B contains an unknown percentage of blue pigment. The mixture of the two inks contains 35 percent blue pigment. What percentage of blue pigment is in ink B?

The 14-milliliter mixture contains 35% blue pigment, so it has 0.35 × 14 = 4.9 milliliters of blue pigment. Ink A contributes 0.10 × 4 = 0.4 milliliters, leaving 4.9 − 0.4 = 4.5 milliliters from ink B. Since ink B totals 10 milliliters, its blue-pigment percentage is 4.5 ÷ 10 = 45%, choice C.

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