2021 TSS Computing P2 Solutions

Sec 4 Computing Prelim 2021 P2 Ans Scheme TASK 1 1 One mark: D4=VLOOKUP(C4,$L$4:$N$30,3,FALSE) One mark: Completing D4:D28 and F4:F28 columns 2m 2 G4=IF(LEN(G4)>0,VLOOKUP(G4,$L$4:$N$30,3,FALSE),0) Note: G4:D28 must be completed appropriately 1m 3 One mark for logical condition, one mark for calculation: I4=IF(AND(LEFT(C4)<>LEFT(E4),LEFT(G4)<>LEFT(E4),LEFT(C4)<>LEFT(G4),LEN(G4)>0) ,0.1*SUM(D4,F4,H4),0) Note: I4:I28 must be completed appropriately 2m 4 J4=SUM(D4,F4,H4)-I4 Note: J4:J28 must be completed appropriately 2m 5 One mark: O4=COUNTIF($C$4:$H$28,L4) One mark: Completing O4:O28 column 1m 6 J30=AVERAGE(J4:J28) 2m 7 1m

TASK 2 8a print("The solutions to this quadratic equation are {} and {}.".format(sol1,sol2)) 1m 8b if sol1==sol2: print("The only solution to this quadratic equation is {}.".format(sol1) else: print("The solutions to this quadratic equation are {} and {}".format(sol1,sol2)) 1 mark for checking if-else, 1 mark for appropriate output 2m 8c if (b**2-4*a*c)<0: print("There are no real solutions to this quadratic equation.") else: sol1 = (-b+(b**2-4*a*c)**0.5)/(2*a) sol2 = (-b-(b**2-4*a*c)**0.5)/(2*a) if sol1==sol2: print("The only solution to this quadratic equation is {}.".format(sol1)) else: print("The solutions to this quadratic equation are {} and {}".format(sol1,sol2)) 1 mark for checking if-else, 1 mark for appropriate output 2m 9a while confirm == "N": : confirm = input("The quadratic equation is {}x^2 + {}x + C = 0, correct? (Y/N):".format(a,b,c)) if confirm == "N": print("Please re-enter the values again.") 1 mark for loop control, 1 mark for formatting of input prompt and output 2m

9b 1 mark for each variable a, b and c, i.e. checking and correcting the equation if a == 1: eqn = "x^2 " elif a == -1: eqn = "-x^2 " else: eqn = str(a) + "x^2 " if b == 1: eqn = eqn + "+ x " elif b == -1: eqn = eqn + "- x " elif b < 0: eqn = eqn + "- " + str(-b) + "x " else: eqn = eqn + "+ " + str(b) + "x " if c < 0: eqn = eqn + "- " + str(-c) else: eqn = eqn + "+ " + str(c) confirm = input("The quadratic equation is {}, correct? (Y/N):".format(eqn)) 3m

TASK 3 10 One mark each: age = 2021 - int(input("Enter your year of birth: ")) allergy = input("Do you have any drug allergies? (Y/N): ") eligible_with_appt = [] eligible_without_appt = [] if age >= 60: if allergy == "N": eligible_without_appt = ["Pfizer-BioNTech"] eligible_without_appt += ["Moderna"] else: eligible_without_appt = ["Novavax"] elif age >= 18: if allergy == "N": eligible_with_appt = ["Pfizer-BioNTech"] eligible_without_appt = ["Moderna"] else: eligible_with_appt = ["Novavax"] elif age >= 12: if allergy == "N": eligible_with_appt = ["Pfizer-BioNTech"] if len(eligible_without_appt) ==0 and len(eligible_with_appt) ==0: print("You are not eligible for any vaccination.") else: print("You are eligible for:") for vaccine in eligible_without_appt: print("- {} vaccine without appointment.".format(vaccine)) for vaccine in eligible_with_appt: print("- {} vaccine with an appointment.".format(vaccine)) 10m ② ② ③ ③ ④ ④ ⑤ ⑥ ⑥ ⑤ ⑦ ⑦ ⑧ ⑦ ⑨ ⑦ ⑩ ⑦ ①

TASK 4 11 One mark each: - loop control (stop iteration only when input is empty) - iteration to run through the input string - checking for the four operators - slicing each number and convert to float - performing the correct operation on the two numbers Sample code: exp=input("Enter an expression: ") while exp !="": for i in range(len(exp)): if exp[i]=="+": result=float(exp[:i])+float(exp[i+1:]) elif exp[i]=="-": result=float(exp[:i])-float(exp[i+1:]) elif exp[i]=="*": result=float(exp[:i])*float(exp[i+1:]) elif exp[i]=="/": result=float(exp[:i])/float(exp[i+1:]) print("="+str(format(result,'.10g'))) exp=input("Enter an expression: ") 5m 12 One mark each: - input with appropriate prompt - output with correct formatting applied Sample Output: Enter an expression: 0.1+0.2 =0.3 Enter an expression: 3-2 =1 Enter an expression: 0.5*6 =3 Enter an expression: 9/3.0 =3 Enter an expression: >>> 2m 13 One mark each: - checking for zero after division - no calculation is performed if division by zero - output an appropriate statement Sample Code: elif exp[i]=="/": if float(exp[i+1:])==0: print("This expression cannot be evaluated.") else: result=float(exp[:i])/float(exp[i+1:]) 3m

14 (a) One mark each: - checking for case of no operators - output the original expression 2m 14 (b) One mark each: - slicing to separate the operators from numbers in the string OR iteration to determine the indices of the operators - slice numbers from the string (and store in a list) and convert to float - iteration to check and perform each operation correctly, from left to right - logic for operating on multiplication & division before addition & subtraction - keeping track of the results of sub-calculations using a new list or update number list - check for division by zero and stop calculation* - output original number if input has no operator* - correct output format, depending on whether division by zero *only awarded if the calculation logic for the 4 operators are correct Sample Code: exp=input("Enter an expression: ") while exp !="": exp_list=[] last=0 for i in range(len(exp)): if exp[i] in "+-*/": exp_list=exp_list+[float(exp[last:i])]+[exp[i]] last=i+1 exp_list=exp_list+[float(exp[last:])] if ("*" in exp_list) or ("/" in exp_list): for i in range(len(exp_list)): if exp_list[i] == "*" or exp_list[i] == "/": if exp_list[i] == "*": exp_list[i+1]=exp_list[i-1]*exp_list[i+1] elif exp_list[i] == "/": if exp_list[i+1]==0: exp_list=[] break else: exp_list[i+1]=exp_list[i-1]/exp_list[i+1] exp_list[i-1]=None exp_list[i]=None exp_list2=[] for item in exp_list: if item != None: exp_list2=exp_list2+[item] for i in range(len(exp_list2)): if exp_list2[i] == "+" or exp_list2[i] == "-": if exp_list2[i] == "+": exp_list2[i+1]=exp_list2[i-1]+exp_list2[i+1] elif exp_list2[i] == "-": exp_list2[i+1]=exp_list2[i-1]-exp_list2[i+1] exp_list2[i-1]=None exp_list2[i]=None if exp_list2==[]: 8m

print("This expression cannot be evaluated.") else: print("="+format(exp_list2[-1],'.10g')) exp=input("Enter an expression: ")