Yesterday Wanda prepared several shipments of lightbulbs and several

Question

﻿Yesterday Wanda prepared several shipments of lightbulbs and several shipments of electrical cords. How many minutes did Wanda spend preparing the shipments of lightbulbs yesterday?

(1) Yesterday the average (arithmetic mean) number of minutes that Wanda spent per shipment of lightbulbs was 20 percent greater than the average number of minutes that she spent per shipment of electrical cords.

(2) Yesterday Wanda spent a total of 90 minutes preparing all of the shipments.

gmatophobia · Accepted Answer

Number of shipments of lightbulbs =  L  
 Number of shipments of electrical cords=  E

Average time taken for one shipment of lightbulb =  t_l  
 Average time taken for one shipment of electrical cord=  t_e

Question:  L*t_l  ?

Statement 1

(1) Yesterday the average (arithmetic mean) number of minutes that Wanda spent per shipment of lightbulbs was 20 percent greater than the average number of minutes that she spent per shipment of electrical cords.

Average time taken for one shipment of lightbulb =  1.2t_e  
 Average time taken for one shipment of electrical cord=  t_e

We don't have any information on the number of shipments ( L ) and the time spent per shipment of an electric chord ( t_e ). Hence, this statement alone is not sufficient. We can eliminate A and D.

Statement 2

(2) Yesterday Wanda spent a total of 90 minutes preparing all of the shipments.

L*t_l + E*t_e = 90

We don't have any information on individual variables. Hence, this statement alone doesn't help us reach a definite answer. We can eliminate B.

Combined

L*1.2*t_e + E*t_e = 90

The information on the number of shipments and the time spent per shipment of electrical cords is missing. Hence, we cannot find a definte answer.

Option E

JeffTargetTestPrep · Answer

We need to answer the question:

total lightbulbs time = ?

Statement One Alone:

=> Yesterday the average (arithmetic mean) number of minutes that Wanda spent per shipment of lightbulbs was 20 percent greater than the average number of minutes that she spent per shipment of electrical cords.

If the average electrical cords time is “e,” then the average lightbulbs time is “1.2e.”

Since no information is given about actual time lengths in minutes, etc., we can’t answer the question.

Statement one is not sufficient. Eliminate answer choices A and D.

Statement Two Alone:

=> Yesterday Wand spent a total of 90 minutes preparing all of the shipments.

Although we know the total time, we don’t know the ratio of total lightbulbs time to total electrical cords time.

Statement two is not sufficient. Eliminate answer choice B.

Statements One and Two Together:

If the number of lightbulbs shipments prepared is “L,” and the number of electrical cords shipments prepared is “E,” then we have:

total lightbulbs time + total electrical cords time = 90 minutes
(1.2e)L + (e)E = 90

We still don’t know the ratio of total lightbulbs time to total electrical cords time, because we have:

(1.2e)L/  = 1.2L/E

The two statements together are not sufficient.

Answer: E

Gemmie · Answer

L = number of lightbulb shipments
C = number of electrical cord shipments
x​ = total time for lightbulbs
y​ = total time for electrical cords

\frac{x}{L}  = average time per lightbulb shipment

\frac{y}{C​}  = average time per electrical cord shipment

Question: x = ?

Statement (1):   \frac{x}{L} = \frac{6}{5} * \frac{y}{C​}

=> Insufficient

Statement (2):  x + y = 90

=> Insufficient

Combining Statements (1) and (2):

\frac{x}{L} = \frac{6}{5} * \frac{y}{C​}

x + y = 90

But we still do not know any about L & C

=> Insufficient

The correct answer is  (E) Both statements together are not sufficient .

MBAApplicant2026 · Answer

Am I missing something here? Given that the average time spent on lightbulb shipments was 20% greater than the average time spent on cord shipments and a total of 90 minutes was spent preparing all the shipments, why can't we conclude that she spent 50 minutes preparing the bulb shipments and 40 minutes preparing the cord shipments?

Bunuel · Answer

Check the highlighted parts. That should help.

Silvio1998 · Answer

The average time per lightbulb spent is 20% greater. Stat1.

Stat2. The total time spent is 90 minutes.

L = # number of lightbulbs (quantity)
E = # number of eletric (quantity)
x = average time spend per lightbulb
y = average time spend per electric 
Z = weighted average

Question asks: LX =?

Formula weighted average = L.X + E.Y / L + E = Z

1) X = 6/5 Y Or Y = 5X/6 
2) LX + EY = 90

Answering your question
  Why can't you assume it is 40 and 50 minutes?
Because you can   not   assume that L = E.

If L = E, then we have LX + LY = 90 
 Y = 5X/6 
LX + L(5X/6) = 90 
(solve algebraically this equation normally.. multiply by 6 everything)
6LX + 5LX = 540
LX = 540/11 = 49 1/11 minutes.. therefore we have an answer, together would be C..

However..   what if L is   DIFFERENT   than E? 
If L = 10 and E = 20, then we have

LX + EY = 90 
Y = 5X/6
L(X) + 20(5X/6) = 90
 (solve algebraically this equation normally.. multiply by 6 everything) 
6LX + 100X = 540
X ( 6L + 100 ) = 540
we assumed L = 10, lets substitute
X (160) = 540 
X = 540/160 = 27/8

We want to answer the question   LX =?   
X = 27/8
L = 10
270/8 = 135/4 is different from 540/11 that we found when L=E.. Since we have this options and many others if we assume different values for L and E.. 
Statements together are not sufficient (E)

Think about the numbers of lightbulbs and the numbers of electric..

egmat · Answer

Looking at this Data Sufficiency question, you're dealing with a classic trap that many students fall into - thinking that having a relationship between averages and a total sum is enough information. Let me walk you through why this isn't the case.

Understanding What We Need

The question asks for a specific number: how many minutes did Wanda spend on lightbulb shipments? This is a value question, so we need to find an exact amount of time.

Analyzing Statement 1

Statement 1 tells us that the average time per lightbulb shipment was 20% greater than the average time per electrical cord shipment.

Let's think about this: if a cord shipment takes  t  minutes on average, then a lightbulb shipment takes  1.2t  minutes. But here's what you need to see - we don't know how many of each type she prepared!

If she prepared many lightbulb shipments and few cord shipments, most of her time went to lightbulbs. But if she prepared few lightbulb shipments and many cord shipments, the opposite is true. Without knowing the counts or the total time, we can't determine the answer.

Statement 1 is NOT sufficient.

Analyzing Statement 2

Statement 2 gives us the total time: 90 minutes for all shipments combined.
Notice how this still doesn't help us - the 90 minutes could be split in countless ways:

Could be 45 minutes on each type
Could be 80 minutes on lightbulbs, 10 on cords
Could be 10 minutes on lightbulbs, 80 on cords

Statement 2 is NOT sufficient.

Combining Both Statements 
Here's where it gets interesting. With both statements, you might think we have enough - we know the relationship between the averages AND the total time. But we're still missing a crucial piece: the number of shipments of each type.
Let me show you with a quick example:

If Wanda prepared 9 lightbulb shipments and 1 cord shipment, with the 20% relationship and 90-minute total, the time on lightbulbs would be about 82 minutes
If she prepared 1 lightbulb shipment and 9 cord shipments, with the same constraints, the time on lightbulbs would be about 11 minutes

These are vastly different answers! Without knowing the shipment counts, we can't determine a unique value.

Answer: E  - Both statements together are insufficient.

Want to master this type of question systematically? You can check out the  step-by-step solution on Neuron by e-GMAT  which reveals the algebraic framework for handling these "missing count" problems and shows you how to quickly identify when shipment/item counts are the missing piece. You can also explore other GMAT official questions with detailed solutions on Neuron for structured practice  here .

Yesterday Wanda prepared several shipments of lightbulbs and several

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Data Sufficiency (DS) Questions

Yesterday Wanda prepared several shipments of lightbulbs and several

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards