Competition Mode Question

John has 13 ten-dollar bills, 11 five-dollar bills, and 17 one-dollar bills. If John needs to pay exactly $128, what is the least number of bills he will need to use?

A. 14
B. 16
C. 17
D. 19
E. 20
_________________

12 ten-dollar bills, 1 five-dollar bills, and 3 one-dollar bills equals $128,......Total no.of bills is 16

OA:B

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John has 13 ten-dollar bills, 11 five-dollar bills, and 17 one-dollar bills. If John needs to pay exactly $128, what is the least number of bills he will need to use?

A. 14
B. 16
C. 17
D. 19
E. 20

To reach near to the amount of $128, ten-dollar bills must be maximum in number such that it satisfies the condition. So,
10 * 13 + 5 * .. does not satisfy as it is more than 128
10 * 12 + 5 * 1 + 1 * 3 = 128 Total 16 bills
10 * 11 + 5 * 3 + 1 * 3 = 128 Total 17 bills [Since 10 = 5 * 2, total number of bills is gong to increase here on-wards because for every decrease in number of ten dollar bills there's an increase of two five dollar bills]
10 * 10 + 5 * 5 + 1 * 3 = 128 Total 18 bills (similar trend as above)

Answer B.
_________________

$128=120+5+3=12•10$+1•5$+3•1$={12+1+3}={16}

Answer (B)

John has 13 ten-dollar bills, 11 five-dollar bills, and 17 one-dollar bills. If John needs to pay exactly $128, what is the least number of bills he will need to use?

Available bills, $ 10 bills = 13, $ 5 bills = 11 and $ 1 bills = 17

Need to pay exactly $ 128 = 12 * $ 10 + 1 * $ 5 + 3 * $ 1= $128

Hence, total least number of bills he will need to use = 12 + 1+ 3 = 16

A. 14
B. 16
C. 17
D. 19
E. 20

Imo. B