A change-making machine contains one-rupee, two-rupee and five-rupee coins. The total number of coins is 300. The amount is Rs. 960. If the numbers of one-rupee coins and two-rupee coins are interchanged, the value comes down by Rs. 40. The total number of five-rupee coins is  Options.
A) 100
B) 140
C) 60
D) 150
E) None of these
Explanation :   Let the number of 5 rupee , 2 rupee and 1 rupee coins be x, y and z respectively.   x + y + z = 300.   5x + 2y + z = 960 .......(i)   5x - y + 2z = 920 ......(ii)   On subtracting (ii) from (i) we get,   y - z = 40.   And, x + 2y = 340.   Using the options,   if x= 140, y= 100 and z= 60, this satisfies all the given conditions.   Answer : 140
<result>B</result>
A change-making machine contains one-rupee, two-rupee and five-rupee coins. The total number of coins is 300. The amount is Rs. 960. If the numbers of one-rupee coins and two-rupee coins are interchanged, the value comes down by Rs. 40. The total number of five-rupee coins is